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CHAPTER 18
SOILS AND FOUNDATIONS
1704.7, 1704.8 and 1704.9 and be conducted in conformance
with Sections 1802.2 through 1802.6. An engineer shall scope,
supervise and approve the classification and subsurface investigation of soil.
1801.2 Design. Allowable bearing pressures, allowable
stresses and design formulas provided in this chapter shall be
used with the allowable stress design load combinations specified in Section 1605.3.
1802.2.1 Questionable soil. Where the safe load-bearing
capacity of the soil is in doubt, or where a load-bearing
value superior to that specified in this code is claimed, the
commissioner shall require that the necessary investigation
be made. Such investigation shall comply with the provisions of Sections 1802.4 through 1802.6.
1. For the design of temporary structures, (defined for this
chapter as a structure that will be in place 180 days or
less) load combinations in Equations 16-8 and‡ 16-9 can
be multiplied by a factor of 0.75.
2. For the design of temporary structures, the Equations
16-10, 16-11 and‡ 16-12 can be multiplied by a factor of
0.67.
3. For any combination of dead loads with three or more
variable loads, these variable loads can be multiplied by
a factor of 0.67.
4. For the combinations of loads to be used in the design of
permanent structures, the load due to lateral earth and
ground-water pressure shall be multiplied by a factor of
1.
1801.2.1 Foundation design for seismic overturning.
Where the foundation is proportioned using the strength
design load combinations of Section 1605.2, the seismic
overturning moment need not exceed 75 percent of the value
computed from Section 9.5.5.6 of ASCE 7 for the equivalent lateral force method, or Section 1618 for the modal
analysis method.
SECTION BC 1802
FOUNDATION AND SOILS INVESTIGATIONS
1802.1 General. Foundation and soils investigations shall be
subject to special inspections in accordance with Sections
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1802.2.3 Seismic Design Category D. Where the structure
is determined to be in Seismic Design Category D in accordance with Section 1616, the soils investigation requirements for Seismic Design Category C, given in Section
1802.2.6, shall be met, in addition to the following:
1. A site-specific analysis in accordance with Sections
1813.2, 1813.3, and 1813.4. Site-specific response
shall be evaluated for site peak ground acceleration
magnitudes and source characteristics consistent with
the design earthquake ground motions.
2. A determination of lateral pressures on basement, cellar, and retaining walls due to earthquake motions.
3. An assessment of potential consequences of any liquefaction and soil strength loss, including estimation
of differential settlement, lateral movement or reduction in foundation soil-bearing capacity, and shall
address mitigation measures. Such measures shall be
given consideration in the design of the structure and
shall include, but are not limited to, ground stabilization, selection of appropriate foundation type and
depths, selection of appropriate structural systems to
accommodate anticipated displacements or any combination of these measures. Peak ground acceleration
shall be determined from a site-specific study taking
into account soil amplification effects, as specified in
Section 1615.2.
Exception: A site-specific study need not be performed provided that peak ground acceleration
equal to SDS/2.5 is used, where SDS is determined
in accordance with Section 1615.
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➡
Where the structural design of soil or foundation members is
based on allowable working stresses, the load reductions as
described in Section 1605.3.1.1 shall be modified to use the
following factors and the design shall be based on the resulting
load values:
➡
Members shall have adequate capacity to resist all applicable combinations of the loads listed in Chapter 16, in accordance with the following:
1802.2.2 Seismic Design Category C. Where a structure is
determined to be in Seismic Design Category C in accordance with Section 1616, an investigation shall be conducted, and shall include an evaluation of the following
potential hazards resulting from earthquake motions: slope
instability, liquefaction and surface rupture due to faulting
or lateral spreading.
➡
The quality and design of materials used structurally in excavations, footings and foundations shall conform to the requirements specified in Chapters 16, 19, 21, 22 and 23 of this code.
Excavations and fills shall also comply with Chapter 33.
1802.2 Where required. The owner or applicant shall submit a
foundation and soils investigation to the commissioner where
required in Sections 1802.2.1 through 1802.2.3.
➡
SECTION BC 1801
GENERAL
1801.1 Scope. The provisions of this chapter shall apply to
building and foundation systems in those areas not subject to
scour or water pressure by wind and wave action. Buildings
and foundations subject to such scour or water pressure loads
shall be designed in accordance with Chapter 16 and Appendix
G of this code.
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SOILS AND FOUNDATIONS
of earlier exploration programs and that meet the requirements of this section may be used as partial fulfillment of the
requirements of this section, subject to the approval of the
commissioner. Additional borings shall be made at the
direction of the engineer responsible for the investigation
when uncertainty exists as to the accuracy of the available
information or specific new project or loading conditions
indicate the need for additional information.
1802.3 Material classification. Soil and rock classification
shall be based on materials disclosed by borings, test pits or
other subsurface exploration methods and shall be determined
in accordance with Tables 1804.1 and 1804.2 and Section
1804.2. Additional laboratory tests shall be conducted to ascertain these classifications where deemed necessary by the engineer responsible for the investigation or the commissioner.
1802.3.1 General. For the purposes of this chapter, the definition and classification of soil materials for use in Table
1804.2 and Section 1804.2 shall be in accordance with
ASTM D 2487.
1802.4 Investigation. Soil classification shall be based on
observation and any necessary tests of the materials disclosed
by borings, test pits or other subsurface exploration made in
appropriate locations. Additional studies shall be made as necessary to evaluate stratigraphy, slope stability, soil strength,
adequacy of load-bearing soils, the effect of moisture variation
on soil-bearing capacity, compressibility, liquefaction and
expansiveness.
1802.4.1 Scope of investigation. The scope of the soil
investigation, including the number, types and depths of
borings or test pits; the equipment used to drill and sample;
the in-situ testing; and the laboratory testing program shall
be determined by the engineer responsible for the investigation. Borings shall be uniformly distributed under the structure or distributed in accordance with load patterns imposed
by the structure. As a minimum, investigations shall include
two exploratory borings for built-over areas up to 5,000
square feet (465 m2), and at least one additional boring for
each additional 2,500 square feet (233 m2), or part thereof,
of built-over areas up to 20,000 square feet (1860 m2). For
built-over areas in excess of 20,000 square feet (1860 m2),
there shall be at least one boring for each additional 5,000
square feet (465 m2), or part thereof. Borings shall be taken
into bedrock, or to an adequate depth below the top of the
load-bearing strata to demonstrate that the foundation loads
have been sufficiently dissipated. For structures having an
average area load (dead plus live) of 1,000 pounds per
square foot (47.9 kN/m2) or more, at least one boring for
every 10,000 square feet (930 m2) of footprint area shall
penetrate at least 100 feet (30 480 mm) below the curb grade
or 5 feet (1524 mm) into bedrock of Class 1c or better,
whichever is less. At least one-half of the borings satisfying
this requirement shall be located within the limits of the
built-up area and the remainder shall be within 25 feet (7620
mm) of the built-up area limits. For structures to be supported on pile foundations, the required number of borings
shall be increased by 30 percent.
1802.4.3 Ground-water table. The subsurface soil investigation shall determine the existing ground-water table.
1802.4.4 Compressible soils. In areas that have compressible soils, the investigation shall determine the extent of
these soils in the plan area of the building and shall determine the preconsolidation pressure and consolidation
parameters of the deposit using appropriate laboratory tests.
The information shall be used in the building’s foundation
design.
1802.5 Soil and rock sampling. The soil boring and sampling
procedures and apparatus shall be in accordance with ASTM D
1586 and ASTM D 1587 and generally accepted engineering
practice. Where liquefaction assessment is performed, the
investigation shall be in accordance with ASTM D 6066. The
rock coring, sampling procedure and apparatus shall be in
accordance with ASTM D 2113 and generally accepted engineering practice. Rock cores shall be obtained with a double-tube core barrel with a minimum outside diameter of 27/8
inches (73 mm). With the approval of the engineer responsible
for the investigation, smaller-diameter double-tube core barrels may be used under special circumstances such as telescoping casing to penetrate boulders, or space limitations requiring
the use of drill rigs incapable of obtaining large-diameter cores.
The engineer responsible for the investigation shall have
a qualified representative on the site inspecting all boring,
sampling, and in-situ testing operations.
Exception: Test pits may be substituted for borings for
one- and two-story structures, and may be used to establish the top of rock, where practical, for taller structures.
In such case, there shall be prepared a test pit observation
report that shall be submitted to the commissioner.
1802.4.2 Existing data. Suitable borings, test pits,
probings, and the logs and records that were obtained as part
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1802.5.1 Bedrock support. Where the foundation design
relies on rock to support footings, piles or caisson sockets, a
sufficient number of rock corings shall extend at least 10
feet (3048 mm) below the lowest level of bearing to provide
assurance of the rock soundness. Where foundations are to
rest on bedrock and such rock is exposed over a part or all of
the area of the building, borings are not required in those
areas where rock is exposed, provided the following
requirements are met:
1. The presence of defects or the inclination of bedding
planes in the rock are of such size and location so as
not to affect stability of the foundation.
2. The foundation is not designed for bearing pressures
exceeding those permitted in Table 1804.2.
1802.5.2 Alternative investigative methods. The engineer
responsible for the investigation may engage specialized
technicians to conduct alternative investigative methods
such as cone penetrometer probing. Data from these investigations may be used to (1) supplement soil boring and rock
coring information, provided there is a demonstrated correlation between the findings, and (2) determine material
properties for static and seismic or liquefaction analyses.
Subject to the approval of the commissioner, alternate
exploration methods may replace borings on a two for one
basis, but in no case shall there be less than two standard
borings for every 10,000 square feet (930 m2) of footprint
area. All the borings shall penetrate at least 100 feet (30 480
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SOILS AND FOUNDATIONS
mm) below the curb grade or 5 feet (1524 mm) into rock
when the average area load equals or exceeds 1,000 pounds
per square foot (48 kPa).
Other in-situ testing methods, such as geophysical, vane
shear, and pressure meter, may be used to determine engineering design parameters, but may not be used as a substitute for the required number of borings.
1802.5.3 Material disposition. Soil and rock samples shall
be maintained in an accessible location, by the permit holder
or owner and made available to the engineer responsible for
the investigation and to the department, until the foundation
work has been completed and accepted, or until 1 year after
the investigation is complete, whichever is longer.
1802.6 Reports. The soil classification and design load-bearing capacity shall be shown on the construction documents.
Where required by the commissioner, the engineer responsible
for the investigation shall sign, seal and submit a written report
of the investigation that includes, but need not be limited to, the
following information:
1. A description of the planned structure.
2. A plot showing the location of test borings and/or excavations.
3. A complete record of the soil sample descriptions.
4. A record of the soil profile.
5. Elevation of the water table, if encountered.
6. Results of in-situ or geophysical testing.
7. Results of laboratory testing.
8. Recommendations for foundation type and design criteria, including but not limited to bearing capacity of
natural or compacted soil; mitigation of the effects of
liquefaction (if applicable); differential settlement and
varying soil strength; and the effects of adjacent loads.
9. Expected total and differential settlement.
10. Pile and pier foundation recommendations and
installed capacities.
11. Special design and construction provisions for footings
or foundations founded on expansive soils, as necessary.
12. Compacted fill material properties and testing in accordance with Section 1803.5.
For pile or pier foundations, the report shall also include:
1. Special installation procedures.
2. Pier and pile load test requirements.
1803.2 Placement of backfill. The excavation outside the
foundation shall be backfilled with soil that is free of organic
material, construction debris, cobbles and boulders or a controlled low-strength material (CLSM). The backfill shall be
placed in lifts and compacted, in a manner that does not damage
the foundation or the waterproofing or damp proofing material.
Exception: Controlled low-strength material need not be
compacted.
1803.3 Site grading. The ground immediately adjacent to the
foundation shall be sloped away from the building as needed,
or an approved alternate method of diverting water away from
the foundation shall be used, where surface water would detrimentally affect the foundation bearing soils. Site grading shall
also comply with Section 1101.11 of the New York City Plumbing Code.
1803.3.1 Seepage. In an excavation where soil and groundwater conditions are such that an inward or upward seepage
might be produced in materials intended to provide vertical
or lateral support for foundation elements or for adjacent
foundations, excavating methods shall control or prevent
the inflow of ground water to prevent disturbance of the soil
material in the excavation or beneath existing buildings. No
foundation shall be placed on soil that has been disturbed by
seepage unless remedial measures have been taken.
1803.4 Grading and fill in floodways. Any floodway
encroachment in areas of special flood hazard shall comply
with Appendix G.
1803.5 Compacted fill material. Where footings will bear on
compacted fill material, the compacted fill shall comply with
the provisions of a geotechnical report, prepared, signed and
sealed by the engineer, which shall contain the following:
1. Specifications for the preparation of the site prior to
placement of compacted fill material.
2. Specifications for material to be used as compacted fill.
3. Test method to be used to determine the maximum dry
density and optimum moisture content of the material to
be used as compacted fill.
4. Maximum allowable thickness of each lift of compacted
fill material.
5. Field test method for determining the in-place dry density of the compacted fill.
6. Minimum acceptable in-place dry density expressed as a
percentage of the maximum dry density determined in
accordance with Item 3.
7. Number and frequency of field tests required to determine compliance with Item 6.
8. Acceptable types of compaction equipment for the specified fill materials.
SECTION BC 1803
EXCAVATION, GRADING AND FILL
1803.1 Excavations near footings or foundations. Excavations for any purpose shall not remove lateral support from any
footing or foundation without first underpinning or protecting
the footing or foundation against settlement or lateral translation.
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1803.6 Controlled low-strength material (CLSM). Where
footings will bear on controlled low-strength material
(CLSM), the CLSM shall comply with the provisions of a
geotechnical report prepared, signed and sealed by the engineer, which shall contain the following:
1. Specifications for the preparation of the site prior to
placement of the CLSM.
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SOILS AND FOUNDATIONS
2. Specifications for the CLSM.
3. Laboratory or field test method(s) to be used to determine the compressive strength or bearing capacity of the
CLSM.
4. Test methods for determining the acceptance of the
CLSM in the field.
5. Number and frequency of field tests required to determine compliance with Item 4.
1803.7 Artificially treated soils. After the treatment procedure, a minimum of one boring shall be made for every 1,600
square feet (149 m2) of that portion of the building that is supported on treated soil, and a sufficient number of samples shall
be recovered from the treated soil to demonstrate the efficacy of
the treatment.
SECTION BC 1804
ALLOWABLE LOAD-BEARING VALUES OF SOILS
1804.1 Design. The presumptive load-bearing values provided
in Table 1804.1 shall be used with the allowable stress design
load combinations specified in Sections 1605.3 and 1801.2.
1804.2 Allowable foundation pressure. The allowable foundation pressure for supporting soils at or near the surface shall
not exceed the values specified in Table 1804.1, unless data to
substantiate the use of a higher value are developed and contained in the engineer’s geotechnical report and subject to the
commissioner’s approval. Allowable bearing pressure shall be
considered to be the pressure at the base of a foundation in
excess of the stabilized overburden pressure existing at the
same level prior to construction operations.
1804.2.1 Classification of materials. Soil materials shall
be classified and identified in accordance with Table
1804.2. In addition, refer to Sections 1804.2.1 through
1804.2.4 for supplementary definitions.
BEDROCK.
a. Hard sound rock (Class 1a). Includes crystalline
rocks, such as gneiss, granite, diabase and schist.
Characteristics are as follows: the rock rings when
struck with pick or bar; {the rock} does not disintegrate after exposure to air or water; {the rock} breaks
with sharp fresh fracture; cracks are unweathered and
less than 1/8-inch (3.2 mm) wide, generally no closer
than 3 feet (914 mm) apart; the RQD (rock quality
designation) with a double tube, NX-size diamond
core barrel is generally 85 percent or greater for each
5-foot (1524 mm) run, or core recovery with BX-size
core is generally 85 percent or greater for each 5-foot
(1524 mm) run.
b. Medium hard rock (Class 1b). Includes crystalline
rocks of paragraph (a) of this subdivision, plus marble
and serpentinite. Characteristics are as follows: all
those listed in paragraph (a) of this subdivision,
except that cracks may be 1/4-inch (6.4 mm) wide and
slightly weathered, generally spaced no closer than 2
feet (610 mm) apart; the RQD with a double tube,
NX-size diamond core barrel is generally between 50
and 85 percent for each 5-foot (1524 mm) run, or core
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recovery with BX-size core is generally 50 to 85 percent for each 5-foot (1524 mm) run.
c. Intermediate rock (Class 1c). Includes rocks
described in paragraphs (a) and (b) of this subdivision, plus cemented shales and sandstone. Characteristics are as follows: the rock gives dull sound when
struck with pick or bar; does not disintegrate after
exposure to air or water; broken pieces may show
weathered surfaces; may contain fracture and weathered zones up to 1 inch (25 mm) wide spaced as close
as 1 foot (305 mm); the RQD with a double tube,
NX-size diamond core barrel is generally 35 to 50
percent for each 5-foot (1524 mm) run, or a core
recovery with BX-size core of generally 35 to 50 percent for each 5-foot (1524 mm) run.
d. Soft rock (Class 1d). Includes rocks described in
paragraphs (a), (b) and (c) of this subdivision in partially weathered condition, plus poorly cemented
shales and sandstones. Characteristics are: rock may
soften on exposure to air or water; may contain thoroughly weathered zones up to 3 inches (76 mm) wide
but filled with stiff soil; the RQD with a double tube,
NX-size diamond core barrel is less than 35 percent
for each 5-foot (1524 mm) run, or core recovery with
BX-size core of generally less than 35 percent for
each 5-foot (1524 mm) run and a standard penetration
resistance more than 50 blows per foot (0.3 meters).
SANDY GRAVEL AND GRAVELS. Consists of
coarse-grained material with more than half of the coarse
fraction larger than the # 4 size sieve and contains little or no
fines (GW and GP). The density of these materials shall be
determined in accordance with the following:
Dense (Class 2a). Those materials having a standard
penetration test N-value greater than 30 blows per 1 foot
(0.3 meter).
Medium (Class 2b). Those materials having a standard
penetration test N-value between 10 and 30 blows per 1
foot (0.3 meter).
Loose (Class 6). Those materials having a standard penetration test N-value less than 10 blows per 1 foot (0.3
meter).
GRANULAR SOILS. These materials are coarse-grained
soils consisting of gravel and/or sand with appreciable
amounts of fines, and gravel (GM, GC, SW, SP, SM, and
SC). The density of granular materials shall be determined
in accordance with the following:
Dense (Class 3a). Those materials having a standard
penetration test N-value greater than 30 blows per 1 foot
(0.3 meter).
Medium (Class 3b). Those materials having a standard
penetration test N-value between 10 and 30 blows per 1
foot (0.3 meter).
Loose (Class 6). Those materials having standard penetration test N-value less than 10 blows per 1 foot (0.3
meter).
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SOILS AND FOUNDATIONS
CLAYS. In the absence of sufficient laboratory data, the
consistency of clay materials (SC, CL, and CH) shall be
determined in accordance with the following:
Hard (Class 4a). Clay requiring picking for removal, a
fresh sample of which cannot be molded by pressure of
the fingers, or having an unconfined compressive
strength in excess of 4 TSF (383 kPa), or standard penetration test N-values greater than 30 blows per 1 foot (0.3
meter).
TABLE 1804.1
ALLOWABLE BEARING PRESSURES
CLASS OF MATERIALS
(Notes 1 and 3)
MAXIMUM ALLOWABLE FOUNDATION
PRESSURE (TSF)
MAXIMUM ALLOWABLE FOUNDATION
PRESSURE (kPa)
1. Bedrock (Notes 2 and 7)
1a Hard sound rock—gneiss, diabase, schist
1b Medium hard rock—marble, serpentine
1c Intermediate rock—shale, sandstone
1d Soft rock—weathered rock
60
40
20
8
5,746
3,830
1,915
766
2. Sandy gravel and gravel (GW, GP)
(Notes 3, 4, 8, and 9)
2a Dense
2b Medium
10
6
958
575
3. Granular soils (GC, GM, SW, SP,SM, and SC)
(Notes 4, 5, 8, and 9)
3a Dense
3b Medium
6
3
575
287
4. Clays (SC, CL, and CH) (Notes 4, 6, 8, and 9)
4a Hard
4b Stiff
4c Medium
5
3
2
479
287
192
3
1.5
287
144
See 1804.2.1
See 1804.2.1
See 1804.2.2 or 1804.2.3
See 1804.2.2 or 1804.2.3
5. Silts and silty soils (ML and MH) (Notes 4, 8, and 9)
5a Dense
5b Medium
6. Organic silts, organic clays, peats, soft clays, loose
granular soils and varved silts
7. Controlled and uncontrolled fills
Notes:
1. Where there is doubt as to the applicable classification of a soil stratum, the allowable bearing pressure applicable to the lower class of material to which the given
stratum might conform shall apply.
2. The tabulated values of allowable bearing pressures apply only for massive rocks or for sedimentary or foliated rocks, where the strata are level or nearly so, and
then only if the area has ample lateral support. Tilted strata and their relation to nearby slopes or excavations shall receive special consideration. The tabulated values for Class 1a materials (hard sound rock) may be increased by 25 percent provided the geotechnical engineer performs additional tests and/or analyses substantiating the increase.
3. For intermediate conditions, values of allowable bearing pressure shall be estimated by interpolation between indicated extremes.
4. Footing embedment in soils shall be in accordance with Section 1805.2 and the width of the loaded area not less than 2 feet (610 mm), unless analysis demonstrates that the proposed construction will have a minimum factor of safety of 2.0 against shear failure of the soil.
5. Estimates of settlements shall govern the allowable bearing value, subject to the maximums given in this table, and as provided in Section 1804.2.
6. The bearing capacity of clay soils shall be established on the basis of the strength of such soils as determined by field or laboratory tests and shall provide a factor
of safety against failure of the soil of not less than 2.0 computed on the basis of a recognized procedure of soils analysis, shall account for probable settlements of
the building and shall not exceed the tabulated maximum values.
7. Increases in allowable bearing pressure due to embedment of the foundation. The allowable bearing values for intermediate to hard rock shall apply where the
loaded area is on the surface of sound rock. Where the loaded area is below the adjacent rock surface and is fully confined by the adjacent rock mass and provided
that the rock mass has not been shattered by blasting or otherwise is or has been rendered unsound, these values may be increased 10 percent of the base value for
each 1 foot (0.3 meters) of embedment below the surface of the adjacent rock surface in excess of 1 foot (0.3 meters), but shall not exceed 200 percent of the values.
8. The allowable bearing values for soils of Classes 2, 3, 4, and 5 determined in accordance with Notes three, four and five above, shall apply where the loaded area is
embedded 4 feet (1219 mm) or less in the bearing stratum. Where the loaded area is embedded more than 4 feet (1219 mm) below the adjacent surface of the bearing stratum, and is fully confined by the weight of the adjacent soil, these values may be increased 5 percent of the base value for each 1-foot (305 mm) additional
embedment, but shall not exceed twice the values. Increases in allowable bearing pressure due to embedment shall not apply to soft rock, clays, silts and soils of
Classes 6 and 7.
9. The allowable bearing values for soils of Classes 2, 3, 4, and 5 determined in accordance with this table and the notes thereto, may be increased up to one-third
where the density of the bearing stratum below the bottom of the footings increases with depth and is not underlain by materials of a lower allowable bearing pressure. Such allowable bearing values shall be demonstrated by a recognized means of analysis that the probable settlement of the foundation due to compression,
and/or consolidation does not exceed acceptable limits for the proposed building.
10. The maximum toe pressure for eccentrically loaded footings may exceed the allowable bearing value by up to 25 percent if it is demonstrated that the heel of the
footing is not subjected to tension.
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Stiff (Class 4b). Clay that can be removed by spading, a
fresh sample of which requires substantial pressure of
the fingers to create an indentation, or having an unconfined compressive strength between 1 TSF (96 kPa) and
4 TSF (383 kPa), or standard penetration test N-values
between 8 and 30 blows per 1 foot (0.3 meter).
Medium (Class 4c). Clay that can be removed by spading, a fresh sample of which can be molded by substantial pressure of the fingers, or having an unconfined
compressive strength between 0.5 TSF (48 kPa) and 1
TSF (96 kPa), or standard penetration test N-values
between 4 and 8 blows per 1 foot (0.3 meter).
Soft (Class 6). Clay, a fresh sample of which can be
molded with slight pressure of the fingers, or having an
unconfined compressive strength less than 0.5 TSF (48
kPa), or standard penetration test N-values less than 4
blows per 1 foot (0.3 meter).
SILTS AND CLAYEY SILTS. In the absence of sufficient
laboratory data, the consistency of silt materials (ML and
MH) shall be determined in accordance with the following:
Dense (Class 5a). Silt with a standard penetration test
N-values greater than 30 blows per 1 foot (0.3 meter).
Medium (Class 5b). Silt with a standard penetration test
N-values between 10 and 30 blows per 1 foot (0.3 meter).
Loose (Class 6). Silt with a standard penetration test
N-values less than 10 blows per 1 foot (0.3 meters).
Organic silts, organic clays, peats, soft clays, loose
granular soils and varved silts. The allowable bearing
pressure shall be determined independently of Table
1804.1 subject to the following:
1. For varved silts, the soil bearing pressure produced
by the proposed building shall not exceed 2 tons
per square foot (192 kPa), except that for desiccated or over consolidated soils, higher bearing
pressures are allowed subject to approval by the
commissioner.
2. For organic silts or clays, soft clays, or for loose
granular soils, the engineer responsible for the
investigation shall establish the allowable soil
bearing pressure based upon the soil’s specific
engineering properties. This may require that the
soils be preconsolidated, artificially treated, or
compacted.
3. A report prepared, signed and sealed by the engineer is required to be filed to substantiate the
design soil pressures to be used on soil materials
and it shall contain, at a minimum:
3.1. Sufficient laboratory test data on the compressible material to indicate the soil
strength and the preconsolidation pressure,
coefficient of consolidation, coefficient of
compressibility, permeability, secondary
376
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compression characteristics, and Atterberg
limits.
3.2. Where the design contemplates improvement of the natural bearing capacity and/or
reduction in settlements by virtue of
preloading: cross sections showing the
amount of fill and surcharge to be placed,
design details showing the required time
for surcharging, and computations showing the amount of settlement to be expected
during surcharging and the estimated
amount and rate of settlement expected to
occur after the structure has been completed, including the influence of dead and
live loads of the structure.
3.3. A detailed analysis showing that the anticipated future settlement will not adversely
affect the performance of the structure.
3.4. Where strip drains, sand drains, or stone
columns are to be used, computations
showing the diameter, spacing, and anticipated method of installation of such drains.
3.5. Records of settlement plate elevations and
pore pressure readings, before, during, and
after surcharging.
1804.2.2 Controlled fills. Fills shall be considered as satisfactory bearing material of the applicable class when placed
in accordance with the following procedures and subject to
the special inspection provisions of Chapter 17:
1. Area to be filled shall be stripped of all organic materials, rubbish and debris.
2. Fill shall not be placed when frozen or on frozen or
saturated subgrade.
3. The engineer, or the engineer’s representative, shall
approve the subgrade prior to fill placement.
4. Fill material shall consist of well graded sand, gravel,
crushed rock, recycled concrete aggregate, or a mixture of these, or equivalent materials with a maximum
of 10 percent passing the #200 sieve, as determined
from the percent passing the #4 sieve.
5. Fill shall be placed and compacted in lifts, not exceeding 12 inches (305 mm), at its optimum moisture content, plus or minus 2 percent, and to not less than a
density of 95 percent of the optimum density as determined by ASTM D 1557.
6. Fill density shall be verified by in-place tests made on
each lift.
7. The allowable bearing value of controlled fill shall be
limited to 3 tons per square foot (383 kPa) providing
the underlying soil is not weaker than the controlled
fill.
2008 NEW YORK CITY BUILDING CODE
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1.
2.
3.
2
Slight to
medium
High to very
high
Inorganic silts, micaceous or
diatomaceous fine sandy or silty soils,
elastic silts.
Inorganic clays of high plasticity, fat
clays.
Organic clays of medium to high
plasticity, organic silts.
MH
CH
OH
Pt
Highly Organic Soils
None to very
slow
None
Slow to none
Slow
Slight to
medium
High
Slight to
medium
Slight
Medium
None
Toughness
(Consistency
near PL)
Give typical name; indicate degree and character of
plasticity; amount and maximum size of coarse
grains; color in wet condition; odor, if any; local or
geologic name and other pertinent descriptive
information; and symbol in parentheses.
For undisturbed soils add information on structure,
stratification, consistency in undisturbed and
remolded states, moisture and drainage conditions
Boundary classifications: Soils possessing characteristics of two groups are designed by combinations of group symbols. For example GM-GC, well-graded gravel-sand mixture with clay binder.
All sieve sizes on this chart are U.S. standard.
Adopted by Corps of Engineers and Bureau of Reclamation, January 1952.
Peat and other highly organic soils.
Slight to
medium
Organic silts and organic silty clays of
low plasticity.
OL
None to very
slow
Quick to slow
Dilatancy
(Reaction to
shaking)
Example:
Silty sand, gravelly; about 20% hard, angular gravel
1
particles /2-in. maximum size; rounded and
subangular sand grains, coarse to fine; about 15%
nonplastic fines with low dry strength; well
compacted and moist in place; alluvial sand; (SM).
Give typical name; indicate approximate percentages
of sand and gravel, maximum size; angularity,
surface condition, and hardness of the coarse grains;
local or geologic name and other pertinent
descriptive information; and symbol in parentheses.
For undisturbed soils add information on
stratification, degree of compactness, cementation,
moisture condition, and drainage characteristics.
6
INFORMATION REQUIRED FOR
DESCRIBING SOILS
Example:
Clayey silt, brown; slightly plastic; small percentage
Readily identified by color, odor, spongy feel and of fine sand; numerous vertical root holes; firm and
dry in place; loess; (ML)
frequently by fibrous texture
Medium to high
Inorganic clays of low to medium
plasticity, gravelly clays, sandy clays,
silty clays, lean clays.
CL
Medium to high
None to slight
Dry Strength
(Crushing
Characteristics)
Identification Procedure on Fraction Smaller than
No. 40 Sieve Size.
Clayey sands, sand-clay mixtures.
SP
SC
Poorly graded sands or gravelly sands, Predominantly one size or a range of sizes with
little or no fines.
some intermediate sizes missing.
SW
Plastic fines
(for identification procedures see CL below).
Wide range in grain size and substantial amounts
of all intermediate particle sizes.
Well-graded sands, gravelly sands,
little or no fines.
GC
Nonplastic fines or fines with low plasticity
(for identification procedures see ML below).
Plastic fines
(for identification procedures see CL below).
Clayey gravels, gravel and clay
mixtures.
GM
Silty sands, sand-silt mixtures.
Nonplastic fines or fines with low plasticity
(for identification procedures see ML below).
Silty gravels, gravel and silt mixtures.
GP
SM
Predominantly one size or a range of sizes with
some intermediate sizes missing.
Poorly graded gravels or gravel-sand
mixture, little or no fines.
GW
5
Wide range in grain size and substantial amounts
of all intermediate particle sizes.
4
3
Well-graded gravels, gravel-sand
mixture, little or no fines.
TYPICAL NAMES
FIELD IDENTIFICATION PROCEDURES
(EXCLUDING PARTICLES LARGER THAN 3
IN. AND BASING FRACTIONS ON ESTIMATED
WEIGHTS)
Inorganic silts and very fine sands,
rock flour, silty or clayey fine sands or
clayey silts with slight plasticity.
1
ML
Fine-grained Soils
Coarse-grained Soils
More than half of material is smaller than No. 200 sieve size.
More than half of material is larger than No. 200 sieve size.
The No. 200 sieve size is about the smallest visible to the naked eye.
1
(For visual classification. the /4-in. size may be used as equivalent to the No. 4 sieve size.)
MAJOR DIVISIONS
Gravels
More than half of coarse fraction is
larger than No. 4 sieve size.
Sands
More than half of coarse fraction is smaller than
No .4 sieve size.
Clean Gravels (Little
or no fines)
Gravels with Fines
(Appreciable amount of
fines)
Clean Sand
(Little or no fines)
Sands with Fines
(Appreciable amount of
fines)
GROUP
SYMBOLS
Limits plotting
in hatched zone
with P1
between 4 and
7 are
borderline
cases requiring
use of dual
symbols.
032058C
LIQUID LIMIT
PLASTICITY CHART
For laboratory classification of
fine-grained soils
Atterberg
limits above
“A” line with
Pl greater than
7
Atterberg
limits above
“A” line or P1
less than 4
Not meeting all gradation
requirements for SW
Above “A” line
with P1
between 4 and
7 are
Atterberg
borderline
limits above
cases requiring
“A” line with
use of dual
P1 greater than symbols.
7
D
Cu = 60 Greater than 6
D10
( D 30 ) 2
Ce =
Between 1 and 3
D10 × D60
Atterberg
limits below
“A” line or P1
less than 4
Not meeting all gradation
requirements for GW
D60
Greater than 4
D10
( D 30 ) 2
Ce =
Between 1 and 3
D10 × D60
Cu =
7
LABORATORY CLASSIFICATION CRITERIA
Plasticity Index
2008 NEW YORK CITY BUILDING CODE
Silts and Clays
Silts and Clays Liquid limit is
Liquid limit is less
greater than 50
than 50
Determine percentage of gravel and sand from grain-size curve. Depending on percentage of fine
(fraction smaller than No. 200 sieve size) coarse-grained soils are classified as follows:
Less than 5%
GW, GP, SW, SP,
More than 12%
GM, GC, SM, SC.
5% to 12%
Borderline cases requiring use of dual symbols.
TABLE 1804.2 UNIFIED SOIL CLASSIFICATION
(Including Identification and Description)
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SOILS AND FOUNDATIONS
377
Use grain-size curve in identifying the fractions as given under field identification.
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SOILS AND FOUNDATIONS
1805.2 Depth of footings. The minimum depth of footings
below the undisturbed ground surface shall be 12 inches (305
mm). Where applicable, the depth of footings shall also conform to Sections 1805.2.1 through 1805.2.3.
1805.2.1 Frost protection. Except where otherwise protected from frost, foundation walls, piers and other permanent supports of buildings and structures shall be protected
from frost by one or more of the following methods:
2. The building area shall be additionally explored using
one standard boring for every 2,500 square foot
(232.3 m2) of building footprint area. These borings
shall be carried to a depth sufficient to penetrate into
natural ground, but not less than 20 feet (6096 mm)
below grade.
1. Extending a minimum of 4 feet (1219 mm) below
grade;
2. Constructing in accordance with ASCE-32; or
3. The fill shall be composed of material that is free of
voids and free of extensive inclusions of mud, organic
materials, such as paper, wood, garbage, cans, or
metallic objects and debris.
1804.2.4 Artificially treated soils. Nominally unsatisfactory soil materials that are artificially compacted, cemented,
or preconsolidated may be used for the support of buildings,
and nominally satisfactory soil materials that are similarly
treated may be used to resist soil bearing pressures in excess
of those indicated in Table 1804.1. The engineer shall
develop treatment plans and procedures and post-treatment
performance and testing requirements and submit such
plans, procedures, and requirements to the commissioner
for approval. After treatment, a sufficient amount of sampling and/or in-situ tests shall be performed in the treated
soil to demonstrate the efficacy of the treatment for the
increased bearing pressure.
➡
Exception: Free-standing buildings meeting all of
the following conditions are shall not required to
be protected:
1. Classified in Structural Occupancy Category I (see Table 1604.5);
2. Area of 400 square feet (37 m2) or less; and
3. Eave height of 10 feet (3048 mm) or less.
Footings shall not bear on frozen soil unless such frozen condition is of a permanent character.
1805.3 Foundations at different levels. Where footings are
supported at different levels, or are at different levels from the
footings of adjacent structures, the influence of the pressures
under the higher footings on the stability of the lower footings
shall be considered in the design. The design shall consider the
requirements for lateral support of the material supporting the
higher footing, the additional load imposed on the lower footings, and assessment of the effects of dragdown on adjacent
pile-supported buildings.
1805.4 Footings. Footings shall be designed and constructed
in accordance with Sections 1805.4.1 through 1805.4.6.
1804.3 Reserved.
SECTION BC 1805
FOOTINGS AND FOUNDATIONS
1805.1 General. Footings and foundations shall be designed
and constructed in accordance with Sections 1805.1 through
1805.9. Footings and foundations shall be built on undisturbed
soil, compacted fill material or CLSM. Compacted fill material
shall be placed in accordance with Section 1803.5. CLSM shall
be placed in accordance with Section 1803.6.
378
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1805.4.1 Design. Footings shall be so designed that the
allowable bearing capacity of the soil is not exceeded, and
that differential settlement is minimized. The minimum
width of footings shall be 18 inches (457 mm).
1805.4.1.1 Design loads. Footings shall be designed for
the most unfavorable effects due to the combinations of
loads specified in Sections 1605.3 and‡ 1801.2. The
dead load shall include the weight of foundations, footings and overlying fill. Reduced live loads, as specified
in Section 1607.9, are permitted to be used in the design
of footings.
1805.4.1.2 Vibratory loads. Where machinery operations or other vibrations are transmitted through the
foundation, consideration shall be given in the footing
design to prevent detrimental disturbances of the soil.
2008 NEW YORK CITY BUILDING CODE
➡
4. The allowable soil bearing pressure on satisfactory
uncontrolled fill material shall not exceed 2 tons per
square foot (192 kPa). One- and two-family dwellings may be founded on satisfactory uncontrolled fill
provided the dwelling site has been explored using at
least one test pit, penetrating at least 8 feet (2438 mm)
below the level of the bottom of the proposed footings, and that the fill has been found to be composed
of material that is free of voids and generally free of
mud and‡ organic materials, such as paper, garbage,
cans, or metallic objects, and debris. Test pits shall be
backfilled with properly compacted fill.
3. Erecting on solid rock.
➡
1. The soil within the building area shall be explored
using test pits at every column. All test pits shall
extend to depths equal to the smaller width of the footing and at least one test pit shall penetrate at least 8
feet (2438 mm) below the level of the bottom of the
proposed footings. All test pits shall be backfilled
with properly compacted fill. Borings may be used in
lieu of test pits, provided that continuous samples of
at least 3 inches (76 mm) in diameter are recovered.
The top surface of footings shall be level. The bottom surface of footings is permitted to have a slope not exceeding one
unit vertical in 10 units horizontal (10-percent slope). Footings
shall be stepped where it is necessary to change the elevation of
the top surface of the footing or where the surface of the ground
slopes more than one unit vertical in 10 units horizontal
(10-percent slope).
➡
1804.2.3 Uncontrolled fills. Fills other than controlled fill
may be considered as satisfactory bearing material of applicable class, subject to the following:
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SOILS AND FOUNDATIONS
Exception: For plain concrete footings supporting
Group R-3 occupancies, the edge thickness is permitted to be 6 inches (152 mm), provided that the footing
does not extend beyond a distance greater than the
thickness of the footing on either side of the supported
wall.
1805.4.2.4 Placement of concrete. Concrete footings
shall not be placed through water unless a tremie or other
method approved by the commissioner is used. Where
placed under or in the presence of water, the concrete
shall be deposited by approved means to ensure minimum segregation of the mix and negligible turbulence of
the water.
➡
➡
➡
1805.4.2.5 Protection of concrete. No foundation shall
be placed on frozen soil. No foundation shall be placed in
freezing weather unless provision is made to maintain
the underlying soil free of frost. Concrete footings shall
be protected from freezing during depositing and for a
period of not less than five days thereafter. Water shall
not be allowed to flow through the deposited concrete.
1805.4.3 Masonry-unit footings. The design, materials
and construction of masonry-unit footings shall comply
with the provisions of Chapter 21.
1805.4.4 Steel grillage footings. Grillage footings of structural steel shapes shall be separated with approved steel
spacers and be entirely encased in concrete with at least 6
inches (152 mm) on the bottom and at least 4 inches (102
mm) at all other points. The spaces between the shapes shall
be completely filled with concrete or cement grout.
1805.4.5 Timber footings. Refer to Chapter 23.
1805.4.6 Wood foundations. Refer to Chapter 23.
2008 NEW YORK CITY BUILDING CODE
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1805.5.2 Foundation wall drainage. Foundation walls
shall be designed to support the weight of the full hydrostatic pressure of undrained backfill unless a drainage system is installed in accordance with Sections 1807.4.2 and
1807.4.3. Foundation walls shall be designed to support the
earth pressures due to the backfill including full hydrostatic
pressure of undrained backfill unless a drainage system is
installed in accordance with Sections 1807.4.2 and
1807.4.3.
1805.5.3 Pier and curtain wall foundations. Except in
Seismic Design Category D, pier and curtain wall foundations are permitted to be used to support light-frame construction not more than two stories in height, provided the
following requirements are met:
1. All load-bearing walls shall be placed on continuous
concrete footings bonded integrally with the exterior
wall footings.
2. The minimum actual thickness of a load-bearing
masonry wall shall not be less than 4 inches (102 mm)
nominal or 35/8 inches (92 mm) actual thickness, and
shall be bonded integrally with piers spaced 6 feet
(1829 mm) on center (o.c.).
3. Piers shall be constructed in accordance with Chapter
21 and the following:
3.1. The unsupported height of the masonry piers
shall not exceed 10 times their least dimension.
3.2. Where structural clay tile or hollow concrete
masonry units are used for piers supporting
beams and girders, the cellular spaces shall be
filled solidly with concrete or Type M or S
mortar.
Exception: Unfilled hollow piers are permitted where the unsupported height of the
pier is not more than four times its least
dimension.
4. The maximum height of a 4-inch (102mm) load-bearing masonry foundation wall supporting wood frame
walls and floors shall not be more than 4 feet (1219
mm) in height.
5. The unbalanced fill for 4-inch (102 mm) foundation
walls shall not exceed 24 inches (610 mm) for solid
masonry, nor 12 inches (305mm) for hollow
masonry.
379
➡
1805.4.2.3 Plain concrete footings. The edge thickness
of plain concrete footings supporting walls of other than
light-frame construction shall not be less than 8 inches
(203 mm) where placed on soil.
1805.5.1.1 Thickness based on walls supported. The
thickness of foundation walls shall not be less than the
thickness of the wall supported, except that foundation
walls of at least 8-inch (203 mm) nominal width are permitted to support brick-veneered frame walls and
10-inch-wide (254 mm) cavity walls.
➡
1805.4.2.2 Footing seismic ties. Where a structure is
assigned to Seismic Design Category D in accordance
with Section 1616, individual spread footings founded
on soil defined in Section 1615.1.1 as Site Class E or F
shall be interconnected by ties. Ties shall be capable of
carrying, in tension or compression, a force equal to the
product of the larger footing load times the seismic coefficient SDS divided by 10 unless it is demonstrated that
equivalent restraint is provided by reinforced concrete
beams within slabs on grade or reinforced concrete slabs
on grade.
1805.5.1 Foundation wall thickness. The minimum thickness of concrete and masonry foundation walls shall comply
with Section 1805.5.1.1.
➡
➡
1805.4.2.1 Concrete strength. Concrete in footings
shall have a specified compressive strength (f'c) of not
less than 2,500 pounds per square inch (psi) (17 237 kPa)
at 28 days.
1805.5 Foundation walls. Concrete and masonry foundation
walls shall be designed in accordance with Chapter 19 or 21,
respectively.
➡
➡
1805.4.2 Concrete footings. The design, materials and construction of concrete footings shall comply with Sections
1805.4.2.1 through 1805.4.2.6 and the provisions of Chapter 19.
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SOILS AND FOUNDATIONS
1807.1.2 Under-floor space. The finished ground level of
an under-floor space such as a crawl space shall not be
located below the bottom of the footings. Where there is evidence that the ground-water table rises to within 6 inches
(152 mm) of the ground level at the outside building perimeter, or that the surface water does not readily drain from the
building site, the ground level of the under-floor space shall
be as high as the outside finished ground level, unless an
approved drainage system is provided. The provisions of
Sections 1802.2.3, 1807.2, 1807.3 and 1807.4 shall not
apply in this case.
Exceptions:
1807.1.2.1 Flood hazard areas. For buildings and structures in areas of special flood hazard, the finished ground
level of an under-floor space such as a crawl space shall
comply with Appendix G.
1. Group R or U occupancies of light-framed construction and two stories or less in height are permitted to
use concrete with a specified compressive strength of
not less than 2,500 psi (17.2 MPa) at 28 days.
1807.1.3 Ground-water control. Where the ground-water
table is lowered and maintained at an elevation not less than
6 inches (152 mm) below the bottom of the lowest floor, the
floor and walls shall be dampproofed in accordance with
Section 1807.2. The design of the system to lower the
ground-water table shall be based on accepted principles of
engineering that shall consider, but not necessarily be limited to, permeability of the soil, rate at which water enters
the drainage system, rated capacity of pumps, head against
which pumps are to operate and the rated capacity of the disposal area of the system.
2. One- and two-family dwellings not more than three
stories in height are not required to comply with the
provisions of ACI 318, Sections 21.10.1 to 21.10.3.
➡
SECTION BC 1806
RETAINING WALLS AND OTHER RETAINING
STRUCTURES
1806.1 General. Retaining walls shall be designed to ensure
stability against overturning, sliding, excessive foundation
pressure and water uplift. Retaining walls shall be designed for
a safety factor of 1.5 against lateral sliding and overturning.
1806.2 Seismic loads on retaining walls and other retaining
structures. Seismic foundation design shall comply with the
requirements of ASCE 7, Section 9.7. The geotechnical analysis and design shall take into consideration the yielding characteristics of the retaining walls or other retaining structures.
1807.2 Dampproofing required. Where hydrostatic pressure
will not occur as determined by Section 1802, floors and walls
for other than wood foundation systems shall be dampproofed
in accordance with this section. Wood foundation systems shall
be constructed in accordance with AFPA TR7.
1807.1 Where required. Walls or portions thereof that retain
earth and enclose interior spaces and floors below grade shall
be waterproofed and dampproofed in accordance with this section, with the exception of those spaces containing occupancy
groups other than residential and institutional where such
omission is not detrimental to the building or occupancy. Ventilation for crawl spaces shall comply with Section 1203.3.
1807.2.1 Floors. Dampproofing materials for floors shall
be installed between the floor and the base course required
by Section 1807.4.1, except where a separate floor is provided above a concrete slab. Where installed beneath the
slab, dampproofing shall consist of not less than 6-mil
(0.006 inch; 0.152 mm) polyethylene with joints lapped not
less than 6 inches (152 mm), or other approved methods or
materials. Where permitted to be installed on top of the slab,
dampproofing shall consist of mopped-on bitumen, not less
than 4-mil (0.004 inch; 0.102 mm) polyethylene, or other
approved methods or materials. Joints in the membrane
shall be lapped and sealed in accordance with the manufacturer's installation instructions.
1807.1.1 Story above grade. Where a basement or cellar is
considered a story above grade and the finished ground level
adjacent to the basement or cellar wall is below the basement or cellar floor elevation for 25 percent or more of the
perimeter, the floor and walls shall be dampproofed in
accordance with Section 1807.2 and a foundation drain
shall be installed in accordance with Section 1807.4.2. The
foundation drain shall be installed around the portion of the
perimeter where the basement or cellar floor is below
1807.2.2 Walls. Dampproofing materials for walls shall be
installed on the exterior surface of the wall, and shall extend
from the top of the footing to above ground level.
Dampproofing shall consist of a bituminous material, 3
pounds per square yard (16 N/m2) of acrylic modified
cement, 1/8-inch (3.2 mm) coat of surface-bonding mortar
complying with ASTM C 887, any of the materials permitted for waterproofing by Section 1807.3.2 or other approved
methods or materials.
SECTION BC 1807
DAMPPROOFING AND WATERPROOFING
380
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2008 NEW YORK CITY BUILDING CODE
➡
For structures assigned to Seismic Design Category D, provisions of ACI 318, Sections 21.10.1 to 21.10.3 shall apply
when not in conflict with the provisions of Section 1805. Concrete shall have a specified compressive strength of not less
than 3,000 psi (20.68 MPa) at 28 days.
➡
See Section 1910 for additional requirements for footings and foundations of structures
assigned to Seismic Design Category C or D.
➡
➡
ground level. The provisions of Sections 1807.3 and
1807.4.1 shall not apply in this case.
1805.6 Reserved.
➡
1805.7 Reserved.
➡
1805.8 Reserved.
➡ 1805.9 Seismic requirements.
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SOILS AND FOUNDATIONS
1807.2.2.1 Surface preparation of walls. Prior to application of dampproofing materials on concrete walls,
holes and recesses resulting from the removal of form
ties shall be sealed with a bituminous material or other
approved methods or materials. Unit masonry walls shall
be parged on the exterior surface below ground level with
not less than 3/8 inch (9.5 mm) of portland cement mortar.
The parging shall be coved at the footing.
dance with Section 1807.1.3 shall be deemed adequate for
lowering the ground-water table.
Exception: Parging of unit masonry walls is not
required where a material is approved for direct application to the masonry.
Exception: Where a site is located in well-drained gravel
or sand/gravel mixture soils, a floor base course is not
required.
➡ 1807.3 Waterproofing required. Where the investigation
➡ required by Section 1802 indicates that a hydro-static pressure
1807.4.2 Foundation drain. A drain that consists of gravel
or crushed stone containing not more than 10-percent material that passes through a No. 4 (4.75 mm) sieve shall be
placed around the perimeter of a foundation. The drain shall
extend a minimum of 12 inches (305 mm) beyond the outside edge of the footing. The thickness shall be such that the
bottom of the drain is not higher than the bottom of the base
under the floor, and that the top of the drain is not less than 6
inches (152 mm) above the top of the footing. The top of the
drain shall be covered with an approved filter membrane
material. Where a drain tile or perforated pipe is used, the
invert of the pipe or tile shall not be higher than the floor elevation. The top of joints or the top of perforations shall be
protected with an approved filter membrane material. The
pipe or tile shall be placed on not less than 2 inches (51 mm)
of gravel or crushed stone complying with Section
1807.4.1, and shall be covered with not less than 6 inches
(152 mm) of the same material.
1807.3.1 Floors. Floors required to be waterproofed shall
be of concrete, designed and constructed to withstand the
hydrostatic pressures to which the floors will be subjected.
Waterproofing shall be accomplished by placing a membrane of rubberized asphalt, butyl rubber, or not less than
6-mil (0.006 inch; 0.152 mm) polyvinyl chloride with joints
lapped not less than 6 inches (152 mm) or other approved
materials under the slab. Joints in the membrane shall be
lapped and sealed in accordance with the manufacturer's
installation instructions.
1807.3.2 Walls. Walls required to be waterproofed shall be
of concrete or masonry and shall be designed and constructed to withstand the hydrostatic pressures and other lateral loads to which the walls will be subjected.
Waterproofing shall be applied from the bottom of the wall
to not less than 12 inches (305 mm) above the maximum elevation of the ground-water table. The remainder of the wall
shall be dampproofed in accordance with Section 1807.2.2.
Waterproofing shall consist of two-ply hot-mopped felts,
not less than 6-mil (0.006 inch; 0.152 mm) polyvinyl chloride, 40-mil (0.040 inch; 1.02 mm) polymer-modified
asphalt, 6-mil (0.006 inch; 0.152 mm) polyethylene or other
approved methods or materials capable of bridging
nonstructural cracks. Joints in the membrane shall be lapped
and sealed in accordance with the manufacturer's installation instructions.
1807.3.2.1 Surface preparation of walls. Prior to the
application of waterproofing materials on concrete or
masonry walls, the walls shall be prepared in accordance
with Section 1807.2.2.1.
1807.3.3 Joints and penetrations. Joints in walls and
floors, joints between the wall and floor and penetrations of
the wall and floor shall be made water-tight utilizing
approved methods and materials.
1807.4 Subsoil drainage system. Where a hydrostatic pressure is to be controlled by a subsoil drainage system,
dampproofing, a floor base course, and subdrains around the
foundation perimeter and under the floor shall be provided. A
subsoil drainage system designed and constructed in accor2008 NEW YORK CITY BUILDING CODE
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1807.4.3 Drainage discharge. The floor base and foundation perimeter drain shall discharge by gravity or mechanical means into an approved drainage system that complies
with the New York City Plumbing Code.
Exception: Where a site is located in well-drained gravel
or sand/gravel mixture soils, a dedicated drainage system
is not required.
1807.5 In-situ walls. Applied waterproofing or dampproofing
need not to be applied to slurry walls or walls constructed
below the water table. In-situ walls shall be constructed with
water-tight joints between individual elements and sealed by
grouting to achieve a uniform water-tight surface. External
drains and waterproofing are not required. In-situ walls constructed using tangent pile or secant pile may require waterproofing systems because their joints cannot be sealed. For
both instances, an under floor seepage collection system or
pressure slab shall be provided.
SECTION BC 1808
PIER AND PILE FOUNDATIONS
1808.1 Definitions. The following words and terms shall, for
the purposes of this section, have the meanings shown herein.
FLEXURAL LENGTH. Flexural length is the length of the
pile from the first point of zero lateral deflection to the underside of the pile cap or grade beam.
PIER FOUNDATIONS. Pier foundations consist of isolated
masonry or cast-in-place concrete structural elements extend381
➡
condition exists, and the design does not include a
ground-water control system as described in Section 1807.1.3,
walls and floors shall be waterproofed in accordance with this
section.
1807.4.1 Floor base course. Floors of basements or cellars,
except as provided for in Section 1807.1.1, shall be placed
over a floor base course not less than 4 inches (102 mm) in
thickness that consists of gravel or crushed stone containing
not more than 10 percent of material that passes through a
No. 4 (4.75 mm) sieve.
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SOILS AND FOUNDATIONS
ing into firm materials. Piers are relatively short in comparison
to their width, with lengths less than or equal to 12 times the
least horizontal dimension of the pier. Piers derive their
load-carrying capacity through skin friction, through end bearing, or a combination of both.
Open-end pipe pile. Steel pipe driven open ended that may
or may not be filled with concrete or soil.
1808.2 Piers and piles—general requirements.
PILE FOUNDATIONS. Pile foundations consist of concrete,
wood or steel structural elements either driven into the ground
or cast in place. Piles are relatively slender in comparison to
their length, with lengths exceeding 12 times the least horizontal dimension. Piles derive their load-carrying capacity through
skin friction, through end bearing, or a combination of both.
Augered-cast-in-place piles. Augered-cast-in-place piles
are constructed by pumping grout into an augered hole during the withdrawal of the auger. The pile is reinforced with a
single reinforcing bar, a reinforcing steel cage or a structural
steel section.
Caisson piles. Steel cased piles are constructed by driving a
steel shell to a water-tight seal at the top of rock and drilling
of an uncased socket within the rock. The shell and socket is
filled with a steel core section and concrete or grout.
Compacted concrete piles. Compacted concrete piles are
constructed by filling a shaft with low-strength concrete as
the casing is withdrawn.
Concrete-filled steel pipe and tube piles. Concrete-filled
steel pipe and tube piles are constructed by driving a steel
pipe or tube section into the soil and filling the pipe or tube
section with concrete. The steel pipe or tube section is left in
place during and after the deposition of the concrete.
Driven uncased piles. Driven uncased piles are constructed
by driving a steel shell into the soil to shore an unexcavated
hole that is later filled with concrete. The steel casing is
lifted out of the hole during the deposition of the concrete.
These piles are allowed only if the concrete is placed under
pressure.
Enlarged base piles. Enlarged base piles are cast-in-place
concrete piles constructed with a base that is larger than the
diameter of the remainder of the pile. The enlarged base is
designed to increase the load-bearing area of the pile in end
bearing. Enlarged base piles include piles installed by driving a precast concrete tip or by compacting concrete into the
base of the pile to form an enlarged base.
H-piles. Steel H-piles are constructed by driving a steel
H-shaped section into the ground.
Steel-cased piles. Steel-cased piles are constructed by driving a steel shell into the soil to shore an unexcavated hole.
The steel casing is left permanently in place and filled with
concrete.
Jacked piles. Steel pipe piles installed by hydraulically
jacking the pile into the ground against a dead-weight reaction. Piles installed by other static forces shall be considered
in this category.
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1808.2.1 Design. Piles are permitted to be designed in
accordance with provisions for piers in Section 1808 and
Sections 1812.3 through 1812.11 where either of the following conditions exists, subject to the approval of the commissioner:
1. Group R-3 and U occupancies not exceeding two stories of light-frame construction, or
2. Where the surrounding foundation materials furnish
adequate lateral support for the pile.
1808.2.2 General. Pier and pile foundations shall be
designed and installed on the basis of a foundation investigation as defined in Section 1802.
The investigation and report provisions of Section 1802
shall be expanded to include, but not be limited to, the following:
1. Recommended pier or pile types and installed capacities.
2. Recommended center-to-center spacing of piers or
piles.
3. Driving criteria.
4. Installation procedures.
5. Field inspection and reporting procedures (to include
procedures for verification of the installed bearing
capacity where required).
6. Pier or pile load test requirements.
7. Durability of pier or pile materials.
8. Designation of bearing stratum or strata.
9. Reductions for group action, where necessary.
Pier and pile foundations shall be designed and installed
under the direct control of an engineer knowledgeable in the
field of geotechnical engineering and pier and pile foundations and shall be subject to special inspection performed
under the direct control of such engineer. The engineer shall
certify to the commissioner that the piers or piles as installed
satisfy the design criteria.
1808.2.3 Special types of piles. The use of types of piles not
specifically mentioned herein is permitted, subject to the
approval of the commissioner, upon the submission of
acceptable test data, calculations and other information
relating to the structural properties and load capacity of such
piles. The allowable stresses shall not in any case exceed the
limitations specified herein.
1808.2.4 Pile caps. Pile caps shall be of reinforced concrete,
and shall include all elements to which piles are connected,
including grade beams and mats. The soil immediately
below the pile cap shall not be considered as carrying any
vertical load. The tops of piles shall be embedded not less
than 3 inches (76 mm) into pile caps and the caps shall
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➡
Belled piers. Belled piers are cast-in-place concrete piers
constructed with a base that is larger than the diameter of the
remainder of the pier. The belled base is designed to
increase the load-bearing area of the pier in end bearing.
Micropiles/minipiles. Small-diameter drilled steel cased
piles, driven uncased piles or caisson piles.
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SOILS AND FOUNDATIONS
1808.2.5 Stability. Piers or piles shall be braced to provide
lateral stability in all directions. Three or more piles connected by a rigid cap shall be considered braced, provided
that the piles are located in radial directions from the centroid of the group not less than 60 degrees (1 rad) apart. A
two-pile group in a rigid cap shall be considered to be
braced along the axis connecting the two piles. Methods
used to brace piers or piles shall be subject to the approval of
the commissioner.
Piles supporting walls shall be driven alternately in lines
spaced at least 1 foot (305 mm) apart and located symmetrically under the center of gravity of the wall load carried,
unless effective measures are taken to provide for eccentricity and lateral forces, or the wall piles are adequately braced
to provide for lateral stability. A single row of piles without
lateral bracing is permitted for one- and two-family dwellings and lightweight construction not exceeding two stories
or 35 feet (10 668 mm) in height, provided the centers of the
piles are located within the width of the foundation wall.
1808.2.6 Structural integrity. Piers or piles shall be
installed in such a manner and sequence as to prevent distortion or damage to piles being installed or already in place to
the extent that such distortion or damage affects the structural integrity of the piles.
1808.2.6.1 Minimum spacing of piles. Piles shall be
spaced to meet the following requirements:
1. Spacing of' piles shall provide for adequate distribution of' the load on the pile group to the supporting soil. In no case shall the minimum
center-to-center spacing of piles be less than 24
inches (610 mm) nor less than the following for the
specific types of piling indicated in this chapter.
2. Minimum spacing between enlarged base concrete
piles shall be 4 feet 6 inches (1372 mm), center to
center except that where the shafts of such piles are
cased for their full length, this spacing may be
reduced to 3 feet 6 inches (1067 mm). Where a
question exists as to possible damage to adjacent
previously driven piles, these minimums shall be
increased. Minimum center-to-center spacing of
piles at the bearing level shall be at least two and
one half times the outside diameter of the shell.
3. Unless special measures are taken to assure that
piles will penetrate sufficiently to meet the
requirements of Section‡1808.2.8 without interfering with or intersecting each other, the minimum center-to-center spacing of piles shall be
twice the average diameter of the butt for round
piles, one and three-quarters times the diagonal for
rectangular piles; or, for taper piles, twice the
diameter at a level two-thirds of the pile length
measured up from the tip.
4. In cases of practical difficulty, the spacing of new
piles from existing piles under an adjacent build2008 NEW YORK CITY BUILDING CODE
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ing may be less than the above values provided that
the requirements relating to minimum embedment
and pile interference are satisfied and that the soil
under the proposed and existing buildings is not
overloaded by the closer pile grouping.
1808.2.6.2 Piles located near a lot line. Piles located
near a lot line shall be designed on the assumption that
the adjacent lot will be excavated to a depth of 10 feet
(3048 mm) below the nearest legally established curb
level. Where such excavation would reduce the embedded length of the pile, the portion of the pile exposed
shall be deemed to provide no lateral or vertical support,
and the load-carrying determination shall be made the
resistance offered by the soil that is subject to potential
excavation has been discounted.
1808.2.7 Splices. Splices shall be constructed so as to provide and maintain true alignment and position of the component parts of the pile during installation and subsequent
thereto and shall be of adequate strength to transmit the vertical and lateral loads (including tensions) and the moments
occurring in the pile section at the location of the splice
without exceeding the allowable stresses for such materials
as established in Section 1809. In all cases splices shall
develop at least 50 percent of the capacity of the pile in
bending. In all cases pile splices situated in the upper 10 feet
(3048 mm) of the pile shall be capable of resisting (at allowable working stresses) the applied moments and shears or
the moment and shear that would result from an assumed
eccentricity of the pile load of 3 inches (76 mm), whichever
is greater. For piles located near a lot line, the embedded
length of such piles shall be determined on the basis that the
adjacent site will be excavated to a depth of 10 feet (3048
mm) below the nearest established curb level as required in
Section 1808.2.6.2.
1808.2.8 Allowable pier or pile loads. Allowable pier or
pile loads shall be determined in accordance with Sections
1808.2.8.1 through 1808.2.8.9.
1808.2.8.1 Determination of allowable loads. The
allowable axial and lateral loads on piers or piles shall be
determined by load tests or a recognized method of analysis. The allowable load shall be determined by a
licensed engineer experienced in geotechnical engineering and shall be approved by the commissioner.
The allowable axial load on a pile shall be the least
value permitted by consideration of the following factors
(for battered piles, the axial load shall be computed from
the resultant of all vertical loads and lateral forces occurring simultaneously):
1. The capacity of the pile as a structural member.
2. The allowable bearing pressure on soil strata
underlying the pile tips.
3. The resistance to penetration of the piles, including resistance to driving, resistance to jacking, the
rate of penetration, or other equivalent criteria.
4. The capacity as indicated by load test, where load
tests are required.
383
➡
extend at least 4 inches (102 mm) beyond the edges of piles.
The tops of piles shall be cut back to sound material before
capping.
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SOILS AND FOUNDATIONS
5. The maximum loads prescribed in Section
1808.2.8.1.3.
may be obtained during construction. All piles shall
penetrate to or into the designated bearing stratum.
1808.2.8.1.1 Bearing capacity. The allowable pile
load shall be limited by the provision that the pressures in materials at and below the pile tips, produced
by the loads on individual piles and by the aggregate
of all piles in a group or foundation, shall not exceed
the allowable bearing values established in Table
1804.1. The transfer of load from piles to soil shall be
determined by a recognized method of analysis. As an
alternative, for purposes of this section, piles or pile
groups may be assumed to transfer their loads to the
underlying materials by spreading the load uniformly
at an angle of 60 degrees (1.04 rad)‡ with the horizontal, starting at a polygon circumscribing the piles,
located as follows:
1808.2.8.1.3 Maximum loads. Except as permitted
by the provisions of Section 1808.2.8.3.1.6, the maximum allowable pile load shall not exceed the values
specified in Table 1808.2.8.1.3.
1. For piles embedded entirely in decomposed
rock or granular soils, or in controlled fill materials, the polygon shall be circumscribed at a
level located two-thirds of the embedded length
of the pile, measured up from the tip.
2. For piles penetrating through silts and clays
into bearing in decomposed rock or granular
soils, the polygon shall be circumscribed at the
bottom of the strata of silts or clays.
1808.2.8.1.4 Minimum pile penetrations. Piles
shall penetrate the minimum distance required to
develop the required load capacity of the pile as established by the required penetration resistance and load
tests as applicable.
1808.2.8.1.5 Capacity as indicated by resistance to
penetration. Where subsurface investigation and
general experience in the area indicate that the soil
that must be penetrated by the pile consists of glacial
deposits containing boulders, or fills containing riprap, excavated detritus, masonry, concrete or other
obstructions in sufficient numbers to present a hazard
to the installation of the piles, the selection of type of
pile and penetration criteria shall be subject to the
approval of the commissioner but in no case shall the
minimum penetration resistance be less than that
stated in Tables 1808.2.8.1.5A and 1802.8.2.8.1.5B.
1808.2.8.1.2 Bearing stratum. The plans for the proposed work shall establish, in accordance with the
requirements relating to allowable bearing pressure,
the bearing stratum to which the piles in the various
sections of the building must penetrate and the
approximate elevations of the top of such bearing
stratum. Where penetration of a given distance into
the bearing strata is required for adequate distribution
of the loads, such penetration shall be shown on the
plans. The indicated elevations of the top of the bearing strata shall be modified by such additional data as
1808.2.8.1.5.1 Piles installed by use of steampowered, air-powered, diesel-powered or
hydraulic impact hammers.
1. The minimum required driving resistance
and the requirements for hammer energies
for various types and capacities of piles are
given in Tables 1808.2.8.1.5A and
1808.2.8.1.5B. To obtain the required total
driving resistance, the indicated driving
resistances shall be added to any driving
resistance experienced by the pile during
installation, but which will be dissipated
TABLE 1808.2.8.1.3
MAXIMUM ALLOWABLE PILE LOADS
TYPE OF PILE
MAXIMUM ALLOWABLE PILE LOAD (TONS)
Caisson Piles
No upper limit
Open-end pipe (or tube) piles bearing on rock of Class 1a, 1b, or 1c
18-in O.D. and greater
14-in to 18-in O.D.
12-in to 14-in
10-in to 12-in
8-in to 10-in
Closed-end pipe (or tube) piles, H-piles, cast-in-place concrete, enlarged base piles,
and precast concrete piles bearing on rock of Class 1a, 1b, or 1c
150
Piles (other than timber piles) bearing on soft rock of Class 1d
80
Piles (other than timber piles) that receive their principal support other than by direct
bearing on rock of Class 1a through 1d
75
Timber piles bearing on rock of Class 1a through 1d
25
Timber piles bearing in suitable soils
250
200
150
100
60
40 tons maximum permissible with load test, 30 tons
maximum without load test.
For SI: 1 ton = 1000 kg.
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SOILS AND FOUNDATIONS
with time (resistance exerted by nonbearing
materials or by materials which are to be
excavated). For the purposes of this section,
the resistance exerted by nonbearing materials may be approximated as the resistance to
penetration of the pile recorded when the
pile has penetrated to the bottom of the lowest stratum of nominally unsatisfactory
bearing material (Class 6 and uncontrolled
fills, but not controlled fill) or to the bottom
of the lowest stratum of soft or loose deposits of soils of Class 4 or 5 but only where
such strata are completely penetrated by the
pile.
2. Alternate for similitude method—The
requirement for installation of piling to the
penetration resistances given in Tables
1808.2.8.1.5A and 1808.2.8.1.5B may be
TABLE 1808.2.8.1.5A
MINIMUM DRIVING RESISTANCE AND MINIMUM HAMMER ENERGY FOR
STEEL H-PILES, PIPE PILES, PRECAST AND CAST-IN-PLACE CONCRETE PILES AND COMPOSITE PILES
(other than timber)
MINIMUM DRIVING RESISTANCE a, c, d, e
Pile Capacity
(tons)
Up to 20
30
40
Hammer Energyb
(ft. lbs.)
Friction Piles
(blows/ft.)
Piles Bearing on Soft Rock
(Class 1d)
(blows/ft.)
15,000
19
48
19,000
15
27
24,000
11
16
15,000
30
72
19,000
23
40
24,000
18
26
15,000
44
96
19,000
32
53
24,000
24
34
15,000
72
120
19,000
49
80
24,000
35
60
32,000
24
40
15,000
96
240
19,000
63
150
24,000
44
100
32,000
30
50
50
Piles Bearing on Rock
(Class 1a, 1b, and 1c)
5 Blows per l/4 inch
(Minimum hammer energy
of 15,000 ft. lbs.)
60
19,000
70 & 80
24,000
32,000
5 Blows per 1/4 inch
(Minimum hammer energy
of 19,000 ft. lbs.)
For SI: 1 foot = 304.8 mm, 1 ton = 1000 kg.
a. Final driving resistance shall be the sum of tabulated values plus resistance exerted by nonbearing materials. The driving resistance of nonbearing materials shall
be taken as the resistance experienced by the pile during driving, but which will be dissipated with time and may be approximated as described in Section
1808.2.8.1.5.1.
b. The hammer energy indicated is the rated energy.
c. Sustained driving resistance. Where piles are to bear in soft rock, the minimum driving resistance shall be maintained for the last 6 inches, unless a higher sustained
driving resistance requirement is established by load test. Where piles are to bear in soil Classes 2 through 5, the minimum driving resistance shall be maintained
for the last that inches unless load testing demonstrates a requirement for higher sustained driving resistance. No pile needs to be driven to a resistance that penetrates in blows per inch (blows per 25 mm) more than twice the resistance indicated in this table, nor beyond the point at which there is no measurable net penetration
under the hammer blow.
d. The tabulated values assume that the ratio of total weight of pile to weight of striking part of the hammer does not exceed 3.5. If a larger ratio is to be used, or for
other conditions for which no values are tabulated, the driving resistance shall be as approved by the commissioner.
e. For intermediate values of pile capacity, minimum requirements for driving resistance may be determined by straight line interpolation.
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385
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SOILS AND FOUNDATIONS
waived where the following six conditions
are satisfied:
2.1. The piles bear on, or in, soil of
Classes 2 through 5.
2.2. The stratigraphy, as defined by not
less than one boring for every 1600
square feet (149 m2) of building area,
shall be reasonably uniform or divisible into areas of uniform conditions.
2.3. Regardless of pile type or capacity,
one load test, as described in Section
1808.2.8.1.5.3, shall be conducted in
each area of uniform conditions, but
not less than two typical piles for the
entire foundation installation of the
building or group of buildings on the
site, nor less than one pile for every
15,000 square feet (1394 m2) of pile
foundation area shall be load tested.
2.4. Except as permitted by the provisions of paragraph 2.6 below, all
building piles within the area of
influence of a given load-tested pile
of satisfactory performance shall be
installed to the same or greater driv-
ing resistance as the successful
load-tested pile. The same or heavier
equipment of the same type that was
used to install the load-tested pile
shall be used to install all other building piles, and the equipment shall be
operated identically. Also, all other
piles shall be of the same type, shape,
external dimension, and equal or
g r e a t e r c r o s s - s e c t i o n as th e
load-tested pile. All building piles
within the area of influence represented by a given satisfactory
load-tested pile shall bear in, or on
the same bearing stratum as the load
test pile.
2.5. A report by an engineer shall be submitted to the commissioner for
review and approval establishing
that the soil-bearing pressures do not
exceed the values permitted by
Table 1804.1 and that the probable
differential settlements will not
cause stress conditions in the building in excess of those permitted by
the provisions of this code.
TABLE 1808.2.8.1.5B
MINIMUM DRIVING RESISTANCE AND HAMMER ENERGY FOR TIMBER PILES
PILE CAPACITY
(TONS)
MINIMUM DRIVING RESISTANCE (BLOWS/IN.)
TO BE ADDED TO DRIVING RESISTANCE
EXERTED BY NONBEARING MATERIALS
(NOTES 1,3,4)
Up to 20
HAMMER ENERGY
(ft./lbs.) (Note 2)
7,500-12,000
9,000-12,000
Over 20 to 25
14,000-16,000
Formula in Note 4 shall apply
Over 25 to 30
12,000-16,000
(single-acting hammers)
Greater than 30
15,000-20,000
(double-acting hammers)
For SI: 1 ton = 1000 kg, 1 inch = 25.4 mm.
Notes:
1. The driving resistance exerted by nonbearing materials is the resistance experienced by the pile during driving, but which will be dissipated with time and may be
approximated as described in Section 1808.2.8.1.5.1.
2. The hammer energy indicated is the rated energy.
3. Sustained driving resistance. Where piles are to bear in soil classes, Soft rock, the minimum driving resistance shall be maintained for the last 6 inches, unless a
higher sustained driving resistance requirement is established by load test. Where piles are to bear in soil Classes 2 through 5, the minimum driving resistance measured in blows per inch (blows per 25 mm) shall be maintained for the last 12 inches unless load testing demonstrates a requirement for higher sustained driving
resistance. No pile need be driven to a resistance that penetrates in blows per inch (blows per 25 mm) more than twice the resistance indicated in this table nor
beyond the point at which there is no measurable net penetration under the hammer blow.
4. The minimum driving resistance shall be determined by the following formula:
P = 2WhH
or
P = 2E
(S + 0.l)
(S+0.l)
where:
P = Allowable pile load in pounds.
Wp = Weight of pile in pounds.
Wh = Weight of striking part of hammer in pounds.
H
E
S
= Actual height of fall of striking part of hammer in feet.
= Rated energy delivered by the hammer per blow in foot/lbs.
= Penetration of pile per blow, in inches, after the pile has been driven to a depth where successive blows produce approximately equal net penetration.
The value Wp shall not exceed three times Wh.
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SOILS AND FOUNDATIONS
2.6. Where the structure of the building
or the spacing and length of the piling is such as to cause the building
and its foundation to act as an essentially rigid body, the building piles
may be driven to length and/or penetration into the bearing stratum without regard to penetration resistance,
subject to the requirement of paragraph 2.5 above, relating to the submission and approval of a report.
1808.2.8.1.5.2 Piles installed by jacking or other
static forces. The carrying capacity of a pile
installed by jacking or other static forces shall be
not more than 50 percent of the load or force used
to install the pile to the required penetration,
except for piles jacked into position for underpinning. The working load of each permanent underpinning pile shall not exceed the larger of the
following values: two-thirds of the total jacking
force used to obtain the required penetration if the
load is held constant for 7 hours without measurable settlement; or one-half of the total jacking
force at final penetration if the load is held for a
period of 1 hour without measurable settlement.
The jacking resistance used to determine the working load shall not include the resistance offered by
nonbearing materials which will be dissipated
with time.
1808.2.8.1.5.3 Piles installed by use of vibratory
hammer. The capacity of piles installed by vibratory hammer shall not exceed the value established
on the principle of similitude, as follows:
1. Comparison piles, as required by the provisions of Item 4 below, shall be installed
using an impact hammer and driving
resistances corresponding to the proposed
pile capacities as determined in paragraph
3‡ below or to tip elevations and driving
resistances as determined by the engineer.
2. For each comparison pile, an identical index
pile shall be installed by use of the vibratory
hammer at a location at least 4 feet (1219
mm), but not more than 6 feet (1829 mm),
from each comparison pile. The index piles
shall be installed to the same tip elevation as
the comparison pile, except that where the
comparison piles bear on rock, the index
piles shall bear in or on similar material. All
driving data for the index pile shall be
recorded.
3. The index piles shall be load tested in accordance with the provisions of Item 4 of this
section. Should the specified load test criteria indicate inadequate capacity of the index
piles, steps 1‡, 2‡, and 3‡ shall be repeated
using longer, larger or other types of piles.
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4. All building piles within the area of influence of a given, satisfactorily tested index
pile shall be installed to the same or lesser
rate of penetration (inches per minute mm
per minute) as the successful index pile. The
same equipment that was used to install the
index pile, identically operated in all
aspects, shall be used to install the building
piles. All building piles shall be of the same
type size and shape as the index pile. All
building piles within the area of influence as
represented by a given satisfactorily tested
index pile shall bear in, or on, the same bearing stratum as the index pile.
1808.2.8.2 Driving criteria. The allowable compressive
load on steel and concrete piles, where determined solely
by the application of an approved wave equation analyses, shall not exceed 40 tons (356 kN). The allowable
compressive loads on timber piles, where determined
soley by the wave equation analysis, shall not exceed 30
tons (267 kN)‡. For allowable loads greater than these
values, the wave equation method of analysis may be
used to establish initial driving criteria, but final driving
criteria and the allowable load shall be verified by load
tests. The delivered energy of the hammer to be used
shall be the maximum consistent with the size, strength
and weight of the driven piles. The use of a follower is
permitted only with the approval of the engineer of
record. The introduction of fresh hammer cushion or pile
cushion material just prior to final penetration is not permitted.
1808.2.8.3 Load tests. Where design compressive loads
per pier or pile are greater than 40 tons (356 kN), [30 tons
(267 kN)‡ for timber piles] or where drilled or jacked
piles are not installed in Class 1a, 1b or 1c material, or
where final penetration is by a vibratory hammer, or
where the design load for any pier or pile foundation is in
doubt, piers or piles shall be load tested in accordance
with this section. At least one pier or pile shall be test
loaded in each area of uniform subsoil conditions.
1808.2.8.3.1 Load test evaluation. It shall be permitted to evaluate pile load tests with any of the following
methods:
1. Davisson Offset Limit.
2. Brinch-Hansen 90 Percent Criterion.
3. Chin-Konder Extrapolation.
4. Other methods approved by the commissioner.
1808.2.8.3.1.1 Additional load tests. Where
required by the commissioner, additional piers or
piles shall be load tested where necessary to establish the allowable capacity. The load capacity shall
be determined by an engineer in accordance with
Section 1808.2.8.3. For friction piles where the
actual production pile lengths vary more than 25
percent from that of the test pile, the engineer shall
require an investigation to determine the adequacy
of the piles.
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1808.2.8.3.1.2 Load test requirements. Before
any load test is made, the proposed apparatus and
structure to be used in making the load test shall be
satisfactory to the commissioner. The test shall be
made under the responsible engineer’s surveillance. A complete record of such tests shall be filed
with the commissioner. Areas of the foundation
site within which the subsurface soil conditions are
substantially similar in character shall be established by the engineer. For piles installed by
impact hammer, one load test shall be conducted in
each area of substantially similar conditions, but
not less than one typical pile for the entire foundation installation of the building or group of buildings on the site occupying a total area of 5,000
2
square feet (465 m ) or less; and not less than two
load tests for a site having a footprint between
5,000 (465 m2) and 30,000 (2787 m2) square feet
and one additional load test for each 20,000 (1860
m2) square feet of added footprint area.
1808.2.8.3.1.3 Load test procedures. Load tests
shall be conducted in accordance with ASTM D
1143 standard procedures and the following conditions:
1. Dial extensometer gages shall provide readings to the nearest 0.001 inch (0.025 mm).
Electrical transducers may be used to make
settlement observations provided that
backup measurements are made utilizing
dial extensometers as described herein at
sufficient times to validate the transducer
readings. The total test load shall remain in
place until the rate of settlement does not
exceed 0.012 inches (0.305 mm) over a time
period of 12 hours. The total load shall be
removed in decrements not exceeding 25
percent of the total load at 1 hour intervals or
longer. In addition to observations required
by ASTM D 1143, settlement observations
shall be performed at 1/2 minute, 1-minute,
2-minute and 4-minute intervals after application of each load increment, and 24 hours
after the entire test load has been removed.
2. Any temporary supporting capacity that the
soil might provide to the pile during a load
test, but which would be dissipated with
time, shall be eliminated by casing off or by
other suitable means, such as increasing the
total test load to account for such temporary
capacity.
1808.2.8.3.1.4 Alternative test methods. Load
test methods other than those described in Section
1808.2.8.3 may be used subject to the approval of
the commissioner where three or more load tests
are required. In such case, at least one alternative
test shall be performed as a calibration on a static
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load tested pile or nearby pile driven to comparable
resistance. No more than one-half the required
number of load tests may be performed by alternative methods. Alternative tests shall be performed
under the supervision of an engineer experienced
in the methods used. The number of alternative
tests shall be at least twice the number of replaced
static load tests.
1808.2.8.3.1.5 Acceptance criteria. The allowable pile load shall be the lesser of the two values
computed as follows:
1. Fifty-percent of the applied load causing a
net settlement of the pile of not more than
one 1/100 of 1 inch per ton (0.25 mm per 8.9
kN) of applied load. Net settlement in this
paragraph is defined as gross settlement due
to the total test load minus the rebound after
removing 100 percent of the test load.
2. Fifty-percent of the applied load causing a
net settlement of the pile of 3/4 inch (19 mm).
Net settlement in this paragraph is defined as
the gross settlement due to the total test load
less the amount of elastic shortening in the
pile section due to total test load. The elastic
shortening shall be calculated as if the pile is
designed as an end-bearing pile or as a friction pile. Alternatively, the net settlement
may be measured directly using a telltale or
other suitable instrumentation.
1808.2.8.3.1.6 Substantiation of higher allowable loads. The pile capacities tabulated in Table
1808.2.8.1.3 may be exceeded where a higher
value can be substantiated on the basis of load tests
and analysis. The provisions of Sections‡
1808.2.8.3.1.2 and 1808.2.8.3.1.3 shall be supplemented, as follows:
The final load increment shall remain in place
for a total of not less than 24 hours; single test piles
shall be subjected to cyclical loading or suitably
instrumented with telltales and strain gauges so
that the movements of the pile tip and butt may be
independently determined and load transfer to the
soil evaluated. A complete record demonstrating
satisfactory performance of the test shall be submitted to the commissioner.
1808.2.8.4 Allowable frictional resistance. The
assumed frictional resistance developed by any pier or
uncased cast-in-place pile shall not exceed one-sixth of
the bearing value of the soil material at minimum depth
as set forth in Table 1804.1, up to a maximum of 500 psf
(24 kPa), unless a greater value is allowed by the commissioner after a soil investigation as specified in Section
1802 is submitted. Frictional resistance and bearing
resistance shall not be assumed to act simultaneously
unless recommended by a soil investigation as specified
in Section 1802.
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➡
1808.2.8.5 Uplift capacity. Where required by the
design, the uplift capacity of a single pier or pile shall be
determined in accordance with accepted engineering
practice based on a minimum factor of safety of three or
by uplift load tests conducted in accordance with ASTM
D 3689. The maximum allowable uplift load shall not
exceed the ultimate load capacity divided by a factor of
safety of two. The design uplift capacities of a pile group
shall not exceed the sum of the design uplift capacities of
the individual piles in the group, nor the uplift capacity
calculating the group action of the pile in accordance
with accepted engineering practice where the calculated
ultimate group capacity is divided by a safety factor of
2.5.
other types and capacities. The requirements of this section apply to the following proposed conditions:
1808.2.8.6 Load-bearing capacity. Piers, individual
piles and groups of piles shall develop ultimate load
capacities of at least twice the design working loads in
the designated load-bearing layers. Analysis shall show
that no soil layer underlying the designated load-bearing
layers causes the load-bearing capacity safety factor to
be less than two and that settlements of strata within the
influence of the pile groups and the average area load of
the supported structure are tolerable for the structure.
4. Support of part of a building on piles and part on
footings.
1808.2.8.7 Bent piers or piles. The load-bearing capacity of piers or piles discovered to have a sharp or sweeping bend shall be determined by an approved method of
analysis in accordance with accepted engineering practice or by load testing a representative pier or pile.
1808.2.8.8 Overloads on piers or piles. The maximum
compressive load on any pier or pile due to mislocation
shall not exceed 110 percent of the allowable design
load. If the total load on any pile, so determined, is in
excess of 110 percent of the allowable load-bearing
capacity, correction shall be made by installing additional piles or by other methods of load distribution as
required to reduce the maximum pile load to 110 percent
of the capacity.
1808.2.8.9 More than one pile type, pile capacity or
method of pile installation. In the conditions described
below, the several parts of the building supported on the
different types, capacities, or modes of piling shall be
separated by suitable joints providing for differential
movement, or analysis shall be prepared by the engineer,
establishing to the satisfaction of the commissioner that
the proposed construction is adequate and safe, and
showing that the probable settlements and differential
settlements to be expected will be tolerable to the structure and not result in instability of the building. The load
test requirements of Sections 1808.2.8.3 shall apply separately and distinctly to each different type or capacity of
piling, method of installation, or type or capacity of
equipment used, except where analysis of the probable,
comparative behavior of the different types or capacities
of the piles or the methods of installation indicates that
data on one type or capacity of pile permit a reliable
extrapolation of the probable behavior of the piles of
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1. Construction of a foundation for a building utilizing piles of more than one type or capacity;
2. Modification of an existing foundation by the
addition of piles of a type or capacity other than
those of the existing piling;
3. Construction or modification of a foundation utilizing different methods or more than one method
of installation, or using different types or capacities of equipment (such as different types of hammers having markedly different striking energies
or speeds); or
1808.2.9 Lateral support.
1808.2.9.1 General. Any soil other than fluid soil shall
be deemed to afford sufficient lateral support to the pier
or pile to prevent buckling and to permit the design of the
pier or pile in accordance with accepted engineering
practice and the applicable provisions of this code.
1808.2.9.2 Unbraced piles. Piles standing unbraced in
air, water or in fluid soils shall be designed as columns in
accordance with the provisions of this code. Such piles
driven into firm ground can be considered fixed and laterally supported at 5 feet (1524 mm) below the ground
surface and in soft material at 10 feet (3048 mm) below
the ground surface unless otherwise prescribed by the
engineer.
1808.2.9.3 Allowable lateral load. Where required by
the design, the lateral load capacity of a pier, a single pile
or a pile group shall be determined by an approved
method of analysis in accordance with accepted engineering practice or by lateral load tests in accordance
with ASTM D 3966 to at least twice the proposed design
working load. The resulting allowable load shall not be
more than one-half of that test load that produces a gross
lateral movement of 1 inch (25mm) at the ground surface.
In the absence of specific project requirements as
determined by the engineer, the resulting allowable load
shall not be more than one-half of that test load that produces a gross lateral movement of 1 inch (25 mm) at the
ground surface. The maximum allowable lateral load of a
pile shall be 1 ton (8.9 kN), unless verified by load test.
Lateral capacities for pile groups shall be modified to
account for group effects in accordance with accepted
engineering practice.
1808.2.10 Allowable stresses in piles and use of higher
allowable pier or pile stresses. Allowable stresses for
designing piles shall be as specified in Sections 1809, 1810,
and 1811. Allowable stresses greater than those specified
for piers or for each pile type in Sections 1809 and 1810 are
permitted where supporting data justifying such higher
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SOILS AND FOUNDATIONS
stresses are filed and approved by the commissioner. Such
substantiating data shall include:
1. A soils investigation in accordance with Section
1802.
2. Pier or pile load tests in accordance with Section
1808.2.8.3, regardless of the load supported by the
pier or pile. The design and installation of the pier or
pile foundation shall be under the direct supervision
of an engineer knowledgeable in the field of soil
mechanics and pier or pile foundations who shall certify to the commissioner that the piers or piles as
installed satisfy the design criteria.
➡
1808.2.11 Piles in subsiding areas. Where piles are driven
through subsiding fills or other subsiding strata and derive
support from underlying firmer materials, consideration
shall be given to the downward frictional forces that may be
imposed on the piles by the subsiding upper strata.
1808.2.12 Settlement analysis. The settlement of piers,
individual piles or groups of piles shall be estimated based
on approved methods of analysis. The predicted settlement
shall cause neither harmful distortion of, nor instability in,
the structure, nor cause any stresses to exceed allowable values.
1808.2.13 Preexcavation. The use of jetting, augering or
other methods of preexcavation shall be subject to the
approval of the commissioner. Where permitted, preexcavation shall be carried out in the same manner as used for piers
or piles subject to load tests and in such a manner that will
not impair the carrying capacity of the piers or piles already
in place or damage adjacent structures. Pile tips shall be
driven below the preexcavated depth until the required resistance or penetration is obtained.
1808.2.14 Installation sequence. Piles shall be installed in
such sequence so as to avoid compacting the surrounding
soil to the extent that other piles cannot be installed properly, and to prevent ground movements that are capable of
damaging adjacent structures.
1808.2.14.1 Protection of adjacent property. Piles and
piers shall be installed with adequate provision for the
protection of adjacent buildings and property.
1808.2.15 Use of vibratory drivers. Vibratory drivers shall
only be used to install piles where the pile is subsequently
seated by an impact hammer to the final driving criteria
established in accordance with Section 1808.2.8.2.
1808.2.16 Pile driveability. Pile cross sections shall be of
sufficient size and strength to withstand driving stresses
without damage to the pile, and to provide sufficient stiffness to transmit the required driving forces.
1808.2.17 Protection of pile materials. Where boring
records or site conditions indicate possible deleterious
action on pier or pile materials because of soil constituents,
changing water levels or other factors, the pier or pile materials shall be adequately protected by materials, methods or
processes approved by the engineer. Protective materials
shall be applied to the piles so as not to be rendered ineffective by driving. The effectiveness of such protective mea390
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sures for the particular purpose shall have been thoroughly
established by satisfactory service records or other evidence. The following specific provisions shall apply:
1. Untreated timber piles shall not be used unless the top
level of the pile is below the permanent water table.
The permanent water table level shall not be assumed
higher than the invert level of sewer, drain, or
subsurface structure in the adjacent streets, nor higher
than the water level at the site resulting from the lowest drawdown of wells or sumps, but in no case shall
untreated timber piles be used where the cut-off level
is less than 10 feet (3048 mm) below the adjacent
legal grade. Where treated piles are required, preservative treatment shall consist of impregnation with
creosote or a creosote solution or CCA treatment. For
p iles en tir e ly em b e d d e d b e lo w g r a d e , a
pentachlorophenal solution may be used. Treatment
shall be in accordance with all requirements of the
AWPA standards and as specified in Section
1809.1.2.
2. Piles installed in ash or garbage fills, cinder fills, and
piles that are free-standing in or near a seawater environment, or that are used for the support of chemical
plants, coal piles and piles under similar conditions of
chemical seepage or aggressive action, or that are
used for support of electrical generating plants, shall
be investigated regarding the need for special protective treatment. Where special protective treatment is
indicated by the engineer, such piles shall be protected against deterioration by encasement, coating or
other device acceptable to the engineer.
1808.2.17.1 Protection of piles during installation.
Piling shall be handled and installed to the required penetration and resistance by methods that leave the piles’
strength unimpaired and that develop and retain their
required load-bearing resistance. Any damaged pile
shall be satisfactorily repaired or the pile shall be
rejected. As an alternative and subject to the approval by
the commissioner, damaged or misaligned piles or piles
not reaching design tip elevation may be used at a
reduced fraction of the design load based on an analysis
by the engineer.
1808.2.17.2 Equipment. Equipment and methods of
installation shall be such that piles are installed in their
proper position and alignment, without damage. Equipment shall be maintained in good working order. The
pile-driving hammer shall travel freely in the leads. The
hammer shall deliver its rated energy and measurements
shall be made of the fall of the ram or other suitable data
shall be obtained at intervals necessary to verify the
actual energy delivered during the final 20 blows of the
hammer.
1808.2.17.3 Cushion or cap block. The cushion or cap
block shall be a solid block of hardwood with its grains
parallel to the axis of the pile and enclosed in a tight-fitting steel housing, or other accepted equivalent assembly. If laminated materials are used, their type and
construction shall be such that their strength is equal to or
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SOILS AND FOUNDATIONS
greater than hardwood. Wood chips, pieces of rope, hose,
shavings, automobile tires or similar materials shall not
be used. Cap block cushions shall be replaced if burned,
crushed, or otherwise damaged. Other cushion materials
may be used subject to the approval of the engineer.
1808.2.17.4 Followers. Followers shall not be used
unless permitted in writing by the engineer responsible
for the pile driving operation. The required driving resistance shall account for the losses of driving energy transmitted to the pile because of the follower. The follower
shall be a single length section, shall be provided with a
socket or hood carefully fitted to the top of the pile to
minimize loss of energy and to prevent damage to the
pile, and shall have sufficient rigidity to prevent “whip”
during driving.
1808.2.18 Use of existing piers or piles. Piers or piles left
in place where a structure has been demolished shall not be
used for the support of new construction unless the piles are
load tested, original installation and testing records are
available, or the new loads are no more than half the calculated previous loads on the piles. The engineer shall determine and certify that the piers or piles are sound and meet
the requirements of this code. The design load applied to
such piers or piles shall be the lowest allowable load as
determined by tests, redriving data or calculations.
1808.2.19 Heaved piles. Piles that have heaved during the
driving of adjacent piles shall be redriven as necessary to
develop the required capacity and penetration, or the capacity of the pile shall be verified by load tests in accordance
with Section 1808.2.8.3.
1808.2.20 Identification. All pier or pile materials shipped
or delivered to the job site shall be identified for conformity
to the specified grade and this identification shall be maintained continuously from the point of manufacture to the
point of installation. Such shipment or delivery shall be
accompanied by a certification from the material supplier or
manufacturer indicating conformance with the construction
documents. Such certification shall be made available to the
engineer of record and the department. In the absence of
adequate data, pier or pile materials shall be tested by an
approved agency to determine conformity to the specified
grade. The approved agency shall furnish a certification of
compliance to the engineer of record, or upon request to the
commissioner.
1808.2.21 Pier or pile location plan. A plan showing the
location and designation of piers or piles by an identification system shall be filed with the commissioner prior to
installation of such piers or piles. Detailed records for piers
or individual piles shall bear an identification corresponding to that shown on the plan.
1808.2.21.1 Tolerance in alignment of the pile axis. If
the axis of any pile is installed out of plumb or deviates
from the specified batter by more than 4 percent of the
pile length, the design of the foundation shall be modified to resist the resulting vertical and lateral forces. In
types of piles for which subsurface inspection is not possible, this determination shall be made on the exposed
section of the pile, which section, at the time of checking
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axial alignment, shall not be less than 2 feet (610 mm) in
length. In piles that can be checked for axial alignment
below the ground surface, the sweep of the pile axis shall
not exceed 4 percent of the embedded length.
1808.2.21.2 Tolerance in the location of the head of
the pile. A tolerance of 3 inches (76 mm) from the
designed location shall be permitted in the installation of
each pile, without reduction in load capacity of the pile
group. Where piles are installed out of position in excess
of this amount, the true loading on such piles shall be
analytically determined from a survey that defines the
actual location of the piles as driven, and using the actual
eccentricity in the pile group with respect to the line of
action of the applied load.
1808.2.22 Special inspection. Special inspections in accordance with Sections 1704.8 and 1704.9 shall be provided
for piles and piers, respectively.
1808.2.23 Seismic design of piers or piles. Seismic design
of piers and piles shall be done in accordance with Sections
1808.2.23.1 through 1808.2.23.2.
1808.2.23.1 Seismic Design Category C. Where a
structure is assigned to Seismic Design Category C in
accordance with Section 1616, individual pile caps, piers
or piles shall be interconnected by ties. Ties shall be
capable of carrying, in tension and compression, a force
equal to the product of the larger pile cap or column load
times the seismic coefficient, SDS, divided by 10 unless
it can be demonstrated that equivalent restraint is provided by reinforced concrete beams within slabs on
grade or reinforced concrete slabs on grade or confinement by competent rock, hard cohesive soils or very
dense granular soils.
Exception: Piers supporting foundation walls, isolated interior posts detailed so the pier is not subject to
lateral loads, and lightly loaded exterior decks and
patios of Group R-3 and U occupancies not exceeding
two stories of light-frame construction, are not subject to interconnection if it can be shown that the soils
are of adequate stiffness, subject to the approval of the
commissioner.
1808.2.23.1.1 Connection to pile cap. Concrete piles
and concrete-filled steel pipe piles shall be connected
to the pile cap by embedding the pile reinforcement or
field-placed dowels anchored in the concrete pile and
the pile cap for a distance equal to the development
length. For deformed bars, the development length is
the full development length for compression or tension, in the case of uplift, without reduction in length
for excess area. Alternative measures for laterally
confining concrete and maintaining toughness and
ductile-like behavior at the top of the pile are permitted provided the design is such that any hinging
occurs in the confined region.
Ends of hoops, spirals and ties shall be terminated
with seismic hooks, as defined in Section 21.1 of ACI
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mum transverse steel ratio for confinement shall not
be less than one-half of that required for columns.
3. Section 21.10.4.4(a) of ACI 318 shall not apply
to concrete piles.
For resistance to uplift forces, anchorage of steel
pipe (round HSS sections), concrete-filled steel pipe
or H-piles to the pile cap shall be made by means other
than concrete bond to the bare steel section.
1808.2.23.2.1 Design details for piers, piles and
grade beams. Piers or piles shall be designed and
constructed to withstand maximum imposed curvatures from earthquake ground motions and structure
response. Curvatures shall include free-field soil
strains modified for soil-pile-structure interaction
coupled with pier or pile deformations induced by lateral pier or pile resistance to structure seismic forces.
Concrete piers or piles on Site Class E or F sites, as
determined in Section 1615.1.1, shall be designed and
detailed in accordance with Sections 21.4.4.1,
21.4.4.2 and 21.4.4.3 of ACI 318 within seven pile
diameters of the pile cap and the interfaces of soft to
medium stiff clay or liquefiable strata. For precast
prestressed concrete piles, detailing provisions as
given in Sections 1809.2.3.2.1 and 1809.2.3.2.2 shall
apply.
Exception: Anchorage of concrete-filled steel
pipe piles is permitted to be accomplished using
deformed bars developed into the concrete portion
of the pile.
Splices of pile segments shall develop the full
strength of the pile, but the splice need not develop the
nominal strength of the pile in tension, shear and
bending when it has been designed to resist axial and
shear forces and moments from the load combinations of Section 1605.4.
1808.2.23.1.2 Design details. Pier or pile moments,
shears and lateral deflections used for design shall be
established considering the nonlinear interaction of
the shaft and soil, as recommended by the engineer.
Where the ratio of the depth of embedment of the
pile-to-pile diameter or width is less than or equal to
six, the pile may be assumed to be rigid.
Pile group effects from soil on lateral pile nominal
strength shall be included where pile center-to-center
spacing in the direction of lateral force is less than
eight pile diameters. Pile group effects on vertical
nominal strength shall be included where pile center-to-center spacing is less than three pile diameters.
The pile uplift soil nominal strength shall be taken as
the pile uplift strength as limited by the frictional
force developed between the soil and the pile.
Where a minimum length for reinforcement or the
extent of closely spaced confinement reinforcement is
specified at the top of the pier or pile, provisions shall
be made so that those specified lengths or extents are
maintained after pier or pile cutoff.
1808.2.23.2 Seismic Design Category D. Where a
structure is assigned to Seismic Design Category D in
accordance with Section 1616, the requirements for
Seismic Design Category C given in Section 1808.2.23.1
shall be met. Provisions of ACI 318, Section 21.10.4,
shall also apply when not in conflict with the provisions
of Sections 1808 through 1812. Concrete shall have a
specified compressive strength of not less than 3,000 psi
(20.68 MPa) at 28 days.
➡
➡
Exceptions:
1. Group R or U occupancies of light-framed construction and two stories or less in height are
permitted to use concrete with a specified compressive strength of not less than 2,500 psi (17.2
MPa) at 28 days.
2. Detached one- and two-family dwellings of
light-frame construction and two stories or less
in height are not required to comply with the
provisions of ACI 318, Section 21.10.4.
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Grade beams shall be designed as beams in accordance with ACI 318, Chapter 21. When grade beams
have the capacity to resist the forces from the load
combinations in Section 1605.4, they need not conform to ACI 318, Chapter 21.
1808.2.23.2.2 Connection to pile cap. For piles
required to resist uplift forces or provide rotational
restraint, design of anchorage of piles into the pile cap
shall be provided considering the combined effect of
axial forces due to uplift and bending moments due to
fixity to the pile cap. Anchorage shall develop a minimum of 25 percent of the strength of the pile in tension. Anchorage into the pile cap shall be capable of
developing the following:
1. In the case of uplift, the lesser of the nominal
tensile strength of the longitudinal reinforcement in a concrete pile, or the nominal tensile
strength of a steel pile, or the pile uplift soil
nominal strength factored by 1.3 or the axial
tension force resulting from the load combinations of Section 1605.4.
2. In the case of rotational restraint, the lesser of
the axial and shear forces, and moments resulting from the load combinations of Section
1605.4 or development of the full axial, bending and shear nominal strength of the pile.
1808.2.23.2.3 Flexural strength. Where the vertical,
lateral-force-resisting elements are columns, the
grade beam or pile cap flexural strengths shall exceed
the column flexural strength.
The connection between batter piles and grade
beams or pile caps shall be designed to resist the nominal strength of the pile acting as a short column. Batter piles and their connections shall be capable of
resisting forces and moments from the load combinations of Section 1605.4.
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SECTION BC 1809
DRIVEN PILE FOUNDATIONS
1809.1 Timber piles. Timber piles shall be designed in accordance with the AF&PA NDS.
1809.1.1 Materials. Round timber piles shall conform to
ASTM D 25. Sawn timber piles shall conform to DOC
PS-20.
1809.1.2 Preservative treatment. Timber piles used to
support permanent structures shall be treated in accordance
with this section unless it is established that the tops of the
untreated timber piles will be below the lowest
ground-water level assumed to exist during the life of the
structure as specified in Section 1808.2.17. Preservative and
minimum final retention shall be in accordance with AWPA
C3 for round timber piles and AWPA C24 for sawn timber
piles. Preservative-treated timber piles shall be subject to a
quality control program administered by an approved
agency. Pile cutoffs shall be treated in accordance with
AWPA M4.
1809.1.3 End-supported piles. Any sudden decrease in
driving resistance of an end-supported timber pile shall be
investigated with regard to the possibility of damage. If the
sudden decrease in driving resistance cannot be correlated
to load-bearing data, the pile shall be removed for inspection or rejected.
1809.1.4 Sizes of piles. Piles shall be of adequate size to
resist the applied loads without creating stresses in the pile
material in excess of 1,200 psi (8.27 MPa) for piles of southern pine, Douglas fir, oak, or other wood of comparable
strength; or 800 psi (5.52 MPa) for piles of cedar, Norway
pine, spruce or other wood of comparable strength. Piles of
25 tons’ (222.5 kN) capacity or more shall have a minimum
8-inch tip (203 mm) with uniform taper. Piles of less than 25
tons’(222.5 kN) capacity shall have a minimum 6-inch (152
mm) tip with uniform taper. All piles, regardless of capacity,
driven to end bearing on bedrock of Classes 1a to 1d and
compact gravels and sands of Class 2a shall have a minimum 8-inch (203 mm) tip and a uniform taper. Any species
of wood may be used that conforms to ASTM D 25 and that
will stand the driving stresses.
engineering practice to resist all stresses induced by handling, driving and service loads.
1809.2.1.2 Minimum dimension. The minimum lateral
dimension shall be 8 inches (203 mm). Corners of square
piles shall be chamfered.
1809.2.1.3 Reinforcement. Longitudinal steel shall be
arranged in a symmetrical pattern and be laterally tied
with steel ties or wire spiral spaced not more than 4
inches (102 mm) apart, center to center, for a distance of
2 feet (610 mm) from the ends of the pile; and not more
than 6 inches (152 mm) elsewhere except that at the ends
of each pile, the first five ties or spirals shall be spaced 1
inch (25mm) center to center. The gage of ties and spirals
shall be as follows:
1. For piles having a diameter of 16 inches (406 mm)
or less, wire shall not be smaller than 0.22 inch (5.6
mm) (No. 5 gage).
2. For piles having a diameter of more than 16 inches
(406 mm) and less than 20 inches (508 mm), wire
shall not be smaller than 0.238 inch (6 mm) (No. 4
gage).
3. For piles having a diameter of 20 inches (508 mm)
and larger, wire shall not be smaller than 1/4 inch
(6.4 mm) round or 0.259 inch (6.6 mm) (No. 3
gage).
1809.2.1.4 Installation. Piles shall be handled and
driven so as not to cause injury or overstressing in a manner that affects durability or strength.
1809.2.2 Precast nonprestressed piles. Precast
nonprestressed concrete piles shall conform to Sections
1809.2.2.1 through 1809.2.2.5.
1809.2.2.1 Materials. Concrete shall have a 28-day
specified compressive strength (f'c) of not less than 3,000
psi (20.68 MPa).
1809.2.2.2 Minimum reinforcement. The minimum
amount of longitudinal reinforcement shall be 0.8 percent of the concrete section and shall consist of at least
four bars.
1809.2.1 General. The materials, reinforcement and installation of precast concrete piles shall conform to Sections
1809.2.1.1 through 1809.2.1.4.
1809.2.2.2.1 Seismic reinforcement in Seismic
Design Category C. Where a structure is assigned to
Seismic Design Category C in accordance with Section 1616, longitudinal reinforcement with a minimum steel ratio of 0.01 shall be provided throughout
the length of precast concrete piles. Within three pile
diameters of the bottom of the pile cap, the longitudinal reinforcement shall be confined with closed ties or
spirals of a minimum 3/8-inch (9.5 mm) diameter. Ties
or spirals shall be provided at a maximum spacing of
eight times the diameter of the smallest longitudinal
bar, not to exceed 6 inches (152 mm). Throughout the
remainder of the pile, the closed ties or spirals shall
have a maximum spacing of 16 times the smallest longitudinal-bar diameter, not to exceed 8 inches (203
mm).
1809.2.1.1 Design and manufacture. Piles shall be
designed and manufactured in accordance with accepted
1809.2.2.2.2 Seismic reinforcement in Seismic
Design Category D. Where a structure is assigned to
1809.1.5 Lagged or inverted piles. The use of lagged or
inverted piles is permitted. Double lagging shall be adequately connected to the basic pile material to transfer the
full pile load from the basic pile material to the lagging without exceeding values of allowable stress as established in
Chapter 23. The connection for single lagging shall be proportioned for half the pile load. The diameter of any inverted
pile at any section shall be adequate to resist the applied load
without exceeding the stresses specified in Section
1809.1.4, but in no case shall it be less than 8 inches (203
mm).
1809.2 Precast concrete piles.
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1809.2.2.4 Installation. A precast concrete pile shall not
be driven before the concrete has attained a compressive
strength of at least 75 percent of the 28-day specified
compressive strength (f'c), but not less than the strength
sufficient to withstand handling and driving forces.
1809.2.2.5 Concrete cover. Reinforcement for piles that
are not manufactured under plant conditions shall have a
concrete cover of not less than 2 inches (51 mm). Reinforcement for piles manufactured under plant control
conditions shall have a concrete cover of not less than 11/4
inches (32 mm) for No. 5 bars and smaller, and not less
than 11/2 inches (38mm) for No. 6 through No. 11 bars
except that longitudinal bars spaced less than 11/2 inches
(38 mm) clear distance apart shall be considered bundled
bars for which the minimum concrete cover shall be
equal to that for the equivalent diameter of the bundled
bars. Reinforcement for piles exposed to seawater shall
have a concrete cover of not less than 3 inches (76 mm).
1809.2.3 Precast prestressed piles. Precast prestressed
concrete piles shall conform to the requirements of Sections
1809.2.3.1 through 1809.2.3.5.
1809.2.3.1 Materials. Prestressing steel shall conform
to ASTM A 416. Concrete shall have a 28-day specified
compressive strength (f 'c) of not less than 5,000 psi
(34.48 MPa).
1809.2.3.2 Design. Precast prestressed piles shall be
designed to resist stresses induced by handling and driving as well as by loads. The effective prestress in the pile
shall not be less than 400 psi (2.76MPa) for piles up to 30
feet (9144 mm) in length, 550 psi (3.79MPa) for piles up
to 50 feet (15 240 mm) in length and 700 psi (4.83 MPa)
for piles greater than 50 feet (15 240 mm) in length.
Effective prestress shall be based on an assumed loss of
30,000 psi (207 MPa) in the prestressing steel. The ten394
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1809.2.3.2.1 Design in Seismic Design Category C.
Where a structure is assigned to Seismic Design Category C in accordance with Section 1616, the minimum volumetric ratio of spiral reinforcement shall
not be less than 0.007 or the amount required by the
following formula for the upper 20 feet (6096 mm) of
the pile.
ρs = 0.12f c /fyh
(Equation 18-4)
where:
f
c
= Specified compressive strength of concrete,
psi (MPa)
fyh
= Yield strength of spiral reinforcement ≤
85,000 psi (586 MPa).
ρs
= Spiral reinforcement index (vol. spiral/vol.
core).
At least one-half the volumetric ratio required by
Equation 18-4 shall be provided below the upper 20 feet
(6096 mm) of the pile.
The pile cap connection by means of dowels as indicated in Section 1808.2.23.1 is permitted. Pile cap connection by means of developing pile reinforcing strand is
permitted provided that the pile reinforcing strand results
in a ductile connection.
1809.2.3.2.2 Design in Seismic Design Category D.
Where a structure is assigned to Seismic Design Category D in accordance with Section 1616, the requirements for Seismic Design Category C in Section
1809.2.3.2.1 shall be met, in addition to the following:
1. Requirements in ACI 318, Chapter 21, do not
apply, unless specifically referenced.
2. Where the total pile length in the soil is 35 feet
(10 668 mm) or less, the lateral transverse reinforcement in the ductile region shall occur
through the length of the pile. Where the pile
length exceeds 35 feet (10 668 mm), the ductile
pile region shall be taken as the greater of 35
feet (10 668 mm) or the distance from the
underside of the pile cap to the point of zero curvature plus three times the least pile dimension.
3. In the ductile region, the center-to-center spacing of the spirals or hoop reinforcement shall
not exceed one-fifth of the least pile dimension,
six times the diameter of the longitudinal
strand, or 8 inches (203 mm), whichever is
smaller.
4. Circular spiral reinforcement shall be spliced
by lapping one full turn and bending the end of
the spiral to a 90-degree hook or by use of a
mechanical or welded splice complying with
Sec. 12.14.3 of ACI 318.
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➡
1809.2.2.3 Allowable stresses. The allowable compressive stress in the concrete shall not exceed 33 percent of
the 28-day specified compressive strength (f 'c) applied to
the gross cross-sectional area of the pile. The allowable
compressive stress in the reinforcing steel shall not
exceed 40 percent of the yield strength of the steel (fy) or a
maximum of 30,000 psi (207 MPa). The allowable tensile stress in the reinforcing steel shall not exceed 50 percent of the yield strength of the steel (fy) or a maximum of
24,000 psi (165 MPa).
sile stress in the prestressing steel shall not exceed the
values specified in ACI 318.
➡
Seismic Design Category D in accordance with Section 1616, the requirements for Seismic Design Category C in Section 1809.2.2.2.1 shall apply except as
modified by this section. Transverse confinement
reinforcement consisting of closed ties or equivalent
spirals shall be provided in accordance with Sections
21.4.4.1, 21.4.4.2 and 21.4.4.3 of ACI 318 within
three pile diameters of the bottom of the pile cap. For
other than Site Class E or F, or liquefiable sites and
where spirals are used as the transverse reinforcement, it shall be permitted to use a volumetric ratio of
spiral reinforcement of not less than one-half that
required by Section 21.4.4.1(a) of ACI 318.
➡
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5. Where the transverse reinforcement consists of
circular spirals, the volumetric ratio of spiral
transverse reinforcement in the ductile region
shall comply with the following:
The hoops and cross ties shall be equivalent to
deformed bars not less than No. 3 in size. Rectangular
hoop ends shall terminate at a corner with seismic
hooks.
ρs = 0.25(f c /fyh)(Ag /Ach - 1.0)[0.5 + 1.4P/(f c Ag)]
Outside of the length of the pile requiring transverse confinement reinforcing, the spiral or hoop
reinforcing with a volumetric ratio not less than
one-half of that required for transverse confinement
reinforcing shall be provided.
(Equation 18-5)
but not less than:
ρs = 0.12(f c/fyh)[0.5 + 1.4P/(f
c
Ag)]
(Equation 18-6)
and need not exceed:
ρs = 0.021
fc = 0.33 f c – 0.27fpc
(Equation 18-7)
where:
Ag = Pile cross-sectional area, square inches
(mm2).
Ach = Core area defined by spiral outside diameter, square inches (mm2).
f
c
1809.2.3.3 Allowable stresses. The maximum allowable design compressive stress, fc, in concrete shall be
determined as follows:
= Specified compressive strength of concrete, psi (MPa)
fyh = Yield strength of spiral reinforcement
≤ 85,000 psi (586 MPa).
P = Axial load on pile, pounds (kN), as determined from Equations 16-5 and 16-6.
ρs = Volumetric ratio (vol. spiral/ vol. core).
6. When transverse reinforcement consists of
rectangular hoops and cross ties, the total
cross-sectional area of lateral transverse reinforcement in the ductile region with spacings,
and perpendicular to dimension, hc, shall conform to:
Ash = 0.3shc (f c /fyh)(Ag /Ach – 1.0)[0.5 + 1.4P/
(f cAg)]
(Equation 18-8)
but not less than:
Ash = 0.12shc (f c /fyh)[0.5 + 1.4P/(f cAg)]
(Equation 18-9)
where:
fyh = ≤ 70,000 psi (483 MPa).
hc = Cross-sectional dimension of pile core
measured center to center of hoop reinforcement, inch (mm).
s = Spacing of transverse reinforcement
measured along length of pile, inch
(mm).
Ash = Cross-sectional area of tranverse reinforcement, square inches (mm2)
f c = Specified compressive strength of concrete, psi (MPa)
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(Equation 18-10)
where:
f ′c = The 28-day specified compressive strength of the
concrete.
fpc = The effective prestress stress on the gross section.
1809.2.3.4 Installation. A prestressed pile shall not be
driven before the concrete has attained a compressive
strength of at least 75 percent of the 28-day specified
compressive strength (f 'c), but not less than the strength
sufficient to withstand handling and driving forces.
1809.2.3.5 Concrete cover. Prestressing steel and pile
reinforcement shall have a concrete cover of not less than
11/4 inches (32 mm) for square piles of 12 inches (305
mm) or smaller size and 11/2 inches (38 mm) for larger
piles, except that for piles exposed to seawater, the minimum protective concrete cover shall not be less than 21/2
inches (64 mm).
1809.3 Structural steel piles. Structural steel piles shall conform to the requirements of Sections 1809.3.1 through
1809.3.4.
1809.3.1 Materials. Structural steel piles, steel pipe and
fully welded steel piles fabricated from plates shall conform
to ASTM A36, ASTM A252, ASTM A283, ASTM A572,
ASTM A 588 or ASTM A 913.
1809.3.2 Allowable stresses. The allowable axial stresses
shall not exceed 35 percent of the minimum specified yield
strength (Fy).
Exception: Where justified in accordance with Section
1808.2.10.1, the allowable axial stress is permitted to be
increased above 0.35Fy, but shall not exceed 0.5Fy.
1809.3.3 Dimensions of H-piles. Sections of H-piles shall
comply with the following:
1. The flange projections shall not exceed 14 times the
minimum thickness of metal in either the flange or the
web and the flange widths shall not be less than 80
percent of the depth of the section.
2. The nominal depth in the direction of the web shall
not be less than 8 inches (203 mm).
3. Flanges and web shall have a minimum nominal
thickness of 3/8 inch (9.5 mm).
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above shall be met. In addition, a minimum longitudinal
reinforcement ratio of 0.005 shall be provided for
uncased cast-in-place drilled or augered concrete piles,
piers or caissons in the top one-half of the pile length, a
minimum length of 10 feet (3048 mm) below ground or
throughout the flexural length of the pile, whichever
length is greatest. The flexural length shall be taken as
the length of the pile to a point where the concrete section
cracking moment strength multiplied by 0.4 exceeds the
required moment strength at that point. There shall be a
minimum of four longitudinal bars with transverse confinement reinforcing provided in the pile in accordance
with Sections 21.4.4.1, 21.4.4.2 and 21.4.4.3 of ACI 318
within three times the least pile dimension of the bottom
of the pile cap. Use of a transverse spiral reinforcing ratio
of not less than one-half of that required in Section
21.4.4.1(a) of ACI 318 for other than Class E, F or
liquefiable sites is allowed. Tie spacing throughout the
remainder of the concrete section shall not exceed
12-longitudinal-bar diameters, one-half the least dimension of the section, nor 12 inches (305 mm). Ties shall be
a minimum of No. 3 bars for piles with a least dimension
up to 20 inches (508 mm), and No. 4 bars for larger piles.
1809.3.4 Dimensions of steel pipe piles. Steel pipe piles
driven open ended shall have a nominal outside diameter of
not less than 8 inches (203 mm). The pipe shall have a minimum of 0.34 square inch (219 mm2) of steel in cross section
to resist each 1,000 foot-pounds (1356 N×m) of pile hammer energy or the equivalent strength for steels having a
yield strength greater than 35,000 psi (241 MPa). Where
pipe wall thickness less than 0.188 inch (4.8 mm) is driven
open ended, a suitable cutting shoe shall be provided.
SECTION 1810
CAST-IN-PLACE CONCRETE PILE FOUNDATIONS
1810.1 General. The materials, reinforcement and installation
of cast-in-place concrete piles shall conform to Sections
1810.1.1 through 1810.1.3.
1810.1.1 Materials. Concrete shall have a 28-day specified
compressive strength (f' c) of not less than 2,500 psi (17.24
MPa). Where concrete is placed through a funnel hopper at
the top of the pile, the concrete mix shall be designed and
proportioned so as to produce a cohesive workable mix having a slump of not less than 4 inches (102 mm) and not more
than 6 inches (152 mm). Where concrete is to be pumped,
the mix design including slump shall be adjusted to produce
a pumpable concrete.
➡
1810.1.2 Reinforcement. Except for steel dowels embedded 5 feet (1524 mm) or less in the pile, reinforcement
where required shall be placed in accordance with Section
1810.3.4 and shall be assembled and tied together and
placed in the pile as a unit before the reinforced portion of
the pile is filled with concrete except in augered uncased
cast-in-place piles. Tied reinforcement in augered uncased
cast-in-place piles shall be placed after piles are filled, while
the grout is still in a semifluid state.
1810.1.2.1 Reinforcement in Seismic Design Category C. Where a structure is assigned to Seismic Design
Category C in accordance with Section 1616, a minimum
longitudinal reinforcement ratio of 0.0025 shall be provided for uncased cast-in-place concrete drilled or
augered piles, piers or caissons in the top one-third of the
pile length, a minimum length of 10 feet (3048 mm)
below the ground or that required by analysis, whichever
length is greatest. The minimum reinforcement ratio, but
no less than that ratio required by rational analysis, shall
be continued throughout the flexural length of the pile.
There shall be a minimum of four longitudinal bars with
closed ties (or equivalent spirals) of a minimum 3/8-inch
(9 mm) diameter provided at 16-longitudinal-bar diameter maximum spacing. Transverse confinement reinforcing with a maximum spacing of the lesser of 6 inches
(152 mm) or 8-longitudinal-bar diameters shall be provided within a distance equal to three times the least pile
dimension of the bottom of the pile cap.
➡
1810.1.3 Concrete placement. Concrete shall be placed in
such a manner as to ensure the exclusion of any foreign matter and to secure a full-sized shaft. Concrete shall not be
placed through water except where a tremie or other
approved method is used. When depositing concrete from
the top of the pile, the concrete shall not be chuted directly
into the pile but shall be poured in a rapid and continuous
operation through a funnel hopper centered at the top of the
pile. Grout for auger cast pile shall be pumped through a
hollow stem auger and shall be maintained throughout
placement.
1810.2 Enlarged base piles. Enlarged base piles shall conform
to the requirements of Sections 1810.2.1 through 1810.2.5.
1810.1.2.2 Reinforcement in Seismic Design Category D. Where a structure is assigned to Seismic Design
Category D in accordance with Section 1616, the
requirements for Seismic Design Category C given
➡
➡
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1810.2.1 Materials. The maximum size for coarse aggregate for concrete shall be 3/4 inch (19.1 mm). Concrete to be
compacted shall have a zero slump.
1810.2.2 Allowable stresses. The maximum allowable
design compressive stress for concrete not placed in a permanent steel casing shall be 25 percent of the 28-day specified compressive strength (f' c). Where the concrete is placed
in a permanent steel casing, the maximum allowable concrete stress shall be 33 percent of the 28-day specified compressive strength (f ' c).
1810.2.3 Installation. Enlarged bases formed either by
compacting concrete or driving a precast base shall be
formed in or driven into granular soils. Piles shall be constructed in the same manner as successful prototype test
piles driven for the project. Pile shafts extending through
peat or other organic soil shall be encased in a permanent
steel casing. Where a cased shaft is used, the shaft shall be
adequately reinforced to resist column action or the annular
space around the pile shaft shall be filled sufficiently to
re-establish lateral support by the soil. Where pile heave
occurs, the pile shall be replaced unless it is demonstrated
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1810.2.5 Concrete cover. The minimum concrete cover
shall be 21/2 inches (64 mm) for uncased shafts and 1 inch
(25 mm) for cased shafts.
1810.3 Drilled or augered uncased piles. Drilled or augered
uncased piles shall conform to Sections 1810.3.1 through
1810.3.5.
1810.3.1 Allowable stresses. The allowable design stress in
the concrete of drilled uncased piles shall not exceed 33 percent of the 28-day specified compressive strength (f' c). The
allowable design stress in the concrete of augered
cast-in-place piles shall not exceed 25 percent of the 28-day
specified compressive strength (f' c). The allowable compressive stress of reinforcement shall not exceed 34 percent
of the yield strength of the steel or 25,500 psi (175.8 Mpa).
➡
1810.3.2 Dimensions. The minimum diameter of drilled or
augered uncased piles shall be 12 inches (305 mm).
1810.3.3 Installation. Where pile shafts are formed
through unstable soils and concrete is placed in an
open-drilled hole, a steel liner shall be inserted in the hole
prior to placing the concrete. Where the steel liner is withdrawn during concreting, the level of concrete shall be
maintained above the bottom of the liner at a sufficient
height to offset any hydrostatic or lateral soil pressure.
Where grout is placed by pumping through a hollow-stem
auger, the auger shall be permitted to rotate in a clockwise
direction during withdrawal. An initial head of grout shall
be established and maintained on the auger flights before
withdrawal. The auger shall be withdrawn in a continuous
manner in increments of about 12 inches (305 mm) each.
Grout pumping pressures shall be measured and maintained
high enough at all times to offset hydrostatic and lateral
earth pressures. Grout volumes shall be measured to ensure
that the volume of grout placed in each pile is equal to or
greater than the theoretical volume of the hole created by the
auger. Where the installation process of any pile is interrupted or a loss of grout pressure occurs, the pile shall be
re-drilled to 5 feet (1524 mm) below the elevation of the tip
of the auger when the installation was interrupted or grout
pressure was lost and reformed. Augered cast-in-place piles
shall not be installed within six pile diameters center to center of a pile filled with concrete or grout less than 12 hours
old, unless approved by the engineer. The level at which
return of the grout occurs during withdrawal shall be
recorded. If the grout level in any completed pile drops during installation of an adjacent pile, the pile shall be replaced.
The installation shall be performed under the direct supervision of the engineer. The engineer shall certify to the commissioner that the piles were installed in compliance with
the approved construction documents.
1810.3.4 Reinforcement. For piles installed with a hollow-stem auger, where full-length longitudinal steel reinforcement is placed without lateral ties, the reinforcement
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Exception: Where physical constraints do not allow the
placement of the longitudinal reinforcement prior to filling the pile with concrete or where partial-length longitudinal reinforcement is placed without lateral ties, the
reinforcement is allowed to be placed after the piles are
completely concreted but while concrete is still in a semifluid state.
1810.3.5 Reinforcement in Seismic Design Category C
or D. Where a structure is assigned to Seismic Design Category C or D in accordance with Section 1616, the corresponding requirements of Sections 1810.1.2.1 and
1810.1.2.2 shall be met.
1810.4 Driven uncased piles. Driven uncased piles shall conform to Sections 1810.4.1 through 1810.4.4.
1810.4.1 Allowable stresses. The allowable design stress in
the concrete shall not exceed 25 percent of the 28-day specified compressive strength (f' c) applied to a cross-sectional
area not greater than the inside area of the drive casing or
mandrel.
1810.4.2 Dimensions. The minimum diameter of the driven
uncased pile shall be 12 inches (305 mm).
1810.4.3 Installation. Piles shall not be driven within six
pile diameters center to center in granular soils or within
one-half the pile length in cohesive soils of a pile filled with
concrete less than 48 hours old unless approved by the commissioner. If the concrete surface in any completed pile rises
or drops, the pile shall be replaced. Piles shall not be
installed in soils that could cause pile heave. The installation
shall be performed under the direct supervision of the engineer who shall certify to the commissioner that the piles
were installed in compliance with the approved design.
1810.4.4 Concrete cover. Pile reinforcement shall have a
concrete cover of not less than 21/2 inches (64 mm), measured from the inside face of the drive casing or mandrel.
1810.5 Steel-cased piles. Steel-cased piles shall comply with
the requirements of Sections 1810.5.1 through 1810.5.4.
1810.5.1 Materials. Pile shells or casings shall be of steel
and shall be sufficiently strong to resist collapse and sufficiently water tight to exclude any foreign materials during
the placing of concrete. Steel shells shall have a sealed tip
with a diameter of not less than 8 inches (203 mm).
1810.5.2 Allowable stresses. The allowable design compressive stress in the concrete shall not exceed 33 percent of
the 28-day specified compressive strength (f' c). The allowable concrete compressive stress shall be 0.40 (f' c) for that
portion of the pile meeting the conditions specified in Sections 1810.5.2.1 through 1810.5.2.4.
1810.5.2.1 Shell thickness. The thickness of the steel
shell shall not be less than manufacturer's standard gage
No. 14 gage (0.068 inch) (1.75 mm) minimum.
1810.5.2.2 Shell type. The shell shall be seamless or provided with seams of strength equal to the basic material
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➡
1810.2.4 Load-bearing capacity. Pile load-bearing capacity shall be verified by load tests in accordance with Section
1808.2.8.3.
shall be placed through ducts in the auger prior to filling the
pile with concrete. All pile reinforcement shall have a concrete cover of not less than 21/2 inches (64 mm).
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that the pile is undamaged and capable of carrying twice its
design load.
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1809.3.4. For mandrel-driven pipe piles, the minimum wall
thickness shall be 1/10 inch (2.5 mm).
1810.5.2.3 Strength. The ratio of steel yield strength (fy)
to 28-day specified compressive strength (f' c) shall not
be less than six.
1810.6.4 Reinforcement. Reinforcement steel shall conform to Section 1810.1.2. Reinforcement shall not be placed
within 1 inch (25 mm) of the steel casing.
1810.5.2.4 Diameter. The nominal pile diameter shall
not be greater than 16 inches (406 mm).
1810.6.4.1 Seismic reinforcement. Where a structure is
assigned to Seismic Design Category C or D in accordance with Section 1616, minimum reinforcement no
less than 0.01 times the cross-sectional area of the pile
concrete shall be provided in the top of the pile with a
length equal to two times the required cap embedment
anchorage into the pile cap, but not less than the tension
development length of the reinforcement. The wall
thickness of the steel pipe shall not be less than 3/16 inch
(5 mm).
1810.5.3 Installation. Steel shells shall be mandrel driven
their full length in contact with the surrounding soil.
The steel shells shall be driven in such order and with
such pacing as to ensure against distortion of or injury to
piles already in place. A pile shall not be driven within four
and one-half average pile diameters of a pile filled with concrete less than 24 hours old unless approved by the commissioner. Concrete shall not be placed in steel shells within
heave range of driving.
1810.5.4 Reinforcement. Reinforcement shall not be
placed within 1 inch (25 mm) of the steel shell. Reinforcing
shall be required for unsupported pile lengths or where the
pile is designed to resist uplift or unbalanced lateral loads.
1810.6.5 Placing concrete. The placement of concrete shall
conform to Section 1810.1.3.
1810.7 Caisson piles. Caisson piles shall conform to the
requirements of Sections 1810.7.1 through 1810.7.9.
1810.5.4.1 Seismic reinforcement. Where a structure is
assigned to Seismic Design Category C or D in accordance with Section 1616, the reinforcement requirements for drilled or augered uncased piles in Section
1810.3.5 shall be met.
1810.7.1 Construction. Caisson piles shall consist of a
shaft section of concrete-filled pipe extending to bedrock
with an uncased socket drilled into the bedrock and filled
with concrete. The caisson pile shall have a full-length
structural steel core or a stub core installed in the rock socket
and extending into the pipe portion a distance equal to the
socket depth.
Exception: A spiral-welded metal casing of a thickness not less than manufacturer’s standard gage No.
14 (0.068 inch) is permitted to provide concrete confinement in lieu of the closed ties or equivalent spirals
required in an uncased concrete pile. Where used as
such, the metal casing shall be protected against possible deleterious action due to soil constituents,
changing water levels or other factors indicated by
boring records of site conditions.
1810.7.2 Materials. Pipe and steel cores shall conform to
the material requirements in Section 1809.3. Pipes shall
have a minimum wall thickness of 3/8 inch (9.5 mm) and
shall be fitted with a suitable steel-driving shoe welded to
the bottom of the pipe. Concrete shall have a 28-day specified compressive strength (f' c) of not less than 4,000 psi
(27.58 MPa). The concrete mix shall be designed and proportioned so as to produce a cohesive workable mix with a
slump of 4 inches to 6 inches (102 mm to 152 mm).
1810.6 Concrete-filled steel pipe and tube piles. Concrete-filled steel pipe and tube piles shall conform to the
requirements of Sections 1810.6.1 through 1810.6.5.
1810.7.3 Design. The depth of the rock socket shall be sufficient to develop the full load-bearing capacity of the caisson
pile with a minimum safety factor of two, but the depth of
the socket in Class 1c rock or better below the shoe shall not
be less than 3 feet (914 mm)‡ of the outside diameter of the
pipe. The minimum outside diameter of the caisson pile
shall be 7 inches (194 mm), and the diameter of the rock
socket shall be approximately equal to the inside diameter
of the pile.
1810.6.1 Materials. Steel pipe and tube sections used for
piles shall conform to ASTM A 252 or ASTM A 283. Concrete shall conform to Section 1810.1.1. The maximum
coarse aggregate size shall be 3/4 inch (19.1 mm).
1810.6.2 Allowable stresses. The allowable design compressive stress in the concrete shall not exceed 33 percent of
the 28-day specified compressive strength (f' c). The allowable design compressive stress in the steel shall not exceed
35 percent of the minimum specified yield strength of the
steel (Fy), provided Fy shall not be assumed greater than
36,000 psi (248 MPa) for computational purposes.
Exception: Where justified in accordance with Section
1808.2.10, the allowable stresses are permitted to be
increased to 0.50 Fy.
1810.6.3 Minimum dimensions. Piles shall have a nominal
outside diameter of not less than 8 inches (203 mm) and a
minimum wall thickness in accordance with Section
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1810.7.4 Structural core. The gross cross-sectional area of
the structural steel core shall not exceed 30 percent of the
gross area of the caisson. The minimum clearance between
the structural core and the pipe shall be 2 inches (51 mm).
Where cores are to be spliced, the ends shall be milled or
ground to provide full contact and shall be full-depth
welded.
1810.7.5 Allowable stresses. The allowable design compressive stresses shall not exceed the following: concrete,
0.33 f' c; steel pipe, 0.35Fy and structural steel core, 0.50Fy.
1810.7.6 Installation. The rock socket and pile shall be
thoroughly cleaned of foreign materials before filling with
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and be of a configuration that will provide confinement
to the cast-in-place concrete.
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concrete. Steel cores shall be set 1 inch (25 mm)‡ above the
base of the rock socket. Concrete shall not be placed through
water except where a tremie or other method approved by
the commissioner is used.
assembly, the concrete reinforcement shall comply with
Sections 1810.1.2.1 and 1810.1.2.2 and the steel section shall
comply with Section 1809.3.4 or 1810.6.4.1.
1810.7.7 Dimensions of caisson piles. Caisson piles shall
consist of concrete pipe piles that are socketed into rock and
constructed with steel reinforcement, and in which the
socket is observed before the concrete is poured. Steel reinforcement shall be covered with at least 11/2 inches (38 mm)
of concrete. The minimum diameter of caisson piles shall be
7 inches (178 mm). A suitable steel driving shoe shall be
welded to the bottom of each caisson pile. The center-to-center spacing of caisson sockets shall be at least two
and one-half times the outside diameter of the shell but not
less than 4 feet (1219 mm).
SECTION BC 1812
PIER FOUNDATIONS
1812.1 General. Isolated and multiple piers used as foundations shall conform to the requirements of Sections 1812.2
through 1812.11, as well as the applicable provisions of Section 1808.2.
1810.7.8 Inspection. All rock sockets shall be inspected to
verify rock quality. Inspection may be accomplished by
direct observation or by video methods or by a core boring
performed prior to the drilling of the socket. Load tests performed in accordance with Section 1808.2.8.3 may be substituted for inspection of rock sockets.
1810.7.9 Caisson piles in soil. Caisson piles as described in
Section 1810.7 may be installed in soil provided that the
socket is formed entirely in soil of Class 4 or better and the
concrete is placed under pressure exceeding 1.5 times the
existing total overburden pressure. The socket shall be
formed by extending the casing to the bottom of the socket
and withdrawing the casing while the concrete is being
pumped under pressure. Piles shall be installed in accordance with the provisions of Sections 1810.3 and 1810.7.
For diameters less than 12 inches (305 mm), the casing
above the socket shall remain in place permanently. Reinforcing to the socket shall be placed in the casing to the
depth of the socket prior to placing concrete.
SECTION BC 1811
COMPOSITE PILES
1811.1 General. Composite piles shall conform to the requirements of Sections 1811.2 through 1811.5.
1811.2 Design. Composite piles consisting of two or more
approved pile types shall be designed to meet the conditions of
installation.
1811.3 Limitation of load. The maximum allowable load shall
be limited by the capacity of the weakest section incorporated
in the pile.
1812.2 Lateral dimensions and height. The minimum dimension of isolated piers used as foundations shall be 2 feet (610
mm), and the height shall not exceed 12 times the least horizontal dimension.
1812.3 Materials. Concrete shall have a 28-day specified compressive strength (f' c) of not less than 2,500 psi (17.24 MPa).
Where concrete is placed through a funnel hopper at the top of
the pier, the concrete mix shall be designed and proportioned so
as to produce a cohesive workable mix having a slump of not
less than 4 inches (102 mm) and not more than 6 inches (152
mm). Where concrete is to be pumped, the mix design including slump shall be adjusted to produce a pumpable concrete.
1812.4 Reinforcement. Except for steel dowels embedded 5
feet (1524 mm) or less in the pier, reinforcement where
required shall be assembled and tied together and shall be
placed in the pier hole as a unit before the reinforced portion of
the pier is filled with concrete.
Exception: Reinforcement is permitted to be wet set and the
21/2 inch (64 mm) concrete cover requirement permitted to
be reduced to 2 inches (51 mm) for Group R-3 and U occupancies not exceeding two stories of light-frame construction, provided the construction method is approved by the
commissioner.
Reinforcement shall conform to the requirements of Sections 1810.1.2.1 and 1810.1.2.2.
Exceptions:
1. Isolated piers supporting posts of Group R-3 and U
occupancies not exceeding two stories of
light-frame construction are permitted to be reinforced as required by rational analysis but not less
than a minimum of one No. 4 bar, without ties or
spirals, when detailed so the pier is not subject to
lateral loads and the soil is determined to be of adequate stiffness.
1811.4 Splices. Splices between concrete and steel or wood
sections shall be designed to prevent separation both before
and after the concrete portion has set, and to ensure the alignment and transmission of the total pile load. Splices shall be
designed to resist uplift caused by upheaval during driving of
adjacent piles, and shall develop the full compressive strength
and not less than 50 percent of the tension and bending strength
of the weaker section.
2. Isolated piers supporting posts and bracing from
decks and patios appurtenant to Group R-3 and U
occupancies not exceeding two stories of
light-frame construction are permitted to be reinforced as required by rational analysis but not less
than one No. 4 bar, without ties or spirals, when the
lateral load, E, to the top of the pier does not exceed
200 pounds (890 N) and the soil is determined to
be of adequate stiffness.
1811.5 Seismic reinforcement. Where a structure is assigned
to Seismic Design Category C or D, in accordance with Section
1616 and where concrete and steel are used as part of the pile
3. Piers supporting the concrete foundation wall of
Group R-3 and U occupancies not exceeding two
stories of light-frame construction are permitted to
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be reinforced as required by rational analysis but
not less than two No. 4 bars, without ties or spirals,
when it can be shown the concrete pier will not
rupture when designed for the maximum seismic
load, Em, and the soil is determined to be of adequate stiffness.
SECTION BC 1813
LIQUEFACTION ANALYSIS
1813.1 General. An assessment of the liquefaction potential
shall be determined for each building site. The evaluation of
liquefaction potential shall include the following considerations:
4. Closed ties or spirals where required by Section
1810.1.2.2 are permitted to be limited to the top 3
feet (914 mm) of the piers 10 feet (3048 mm) or
less in depth supporting Group R-3 and U occupancies of Seismic Design Category D, not
exceeding two stories of light-frame construction.
1812.5 Concrete placement. Concrete shall be placed in such
a manner as to ensure the exclusion of any foreign matter and to
secure a full-sized shaft. Concrete shall not be placed through
water except where a tremie or other approved method is used.
When depositing concrete from the top of the pier, the concrete
shall not be chuted directly into the pier but shall be poured in a
rapid and continuous operation through a funnel hopper centered at the top of the pier.
1812.6 Belled bottoms. Where pier foundations are belled at
the bottom, the edge thickness of the bell shall not be less than
that required for the edge of footings. Where the sides of the
bell slope at an angle less than 60 degrees (1 rad) from the horizontal, the effects of vertical shear shall be considered.
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1812.7 Reserved.
1812.8 Concrete. Where adequate lateral support is not provided, and the ratio of unsupported height to least lateral
dimension does not exceed three, piers of plain concrete shall
be designed and constructed as pilasters in accordance with
ACI 318. Where the unsupported height to least lateral dimension exceeds three, piers shall be constructed of reinforced concrete, and shall conform to the requirements for columns in
ACI 318.
Exception: Where adequate lateral support is furnished by
the surrounding materials as defined in Section 1808.2.9,
piers are permitted to be constructed of plain or reinforced
concrete. The requirements of ACI 318 for bearing on concrete shall apply.
1. Noncohesive soils below ground-water table and less
than 50 feet (15 240 mm) below the ground surface shall
be considered to have potential for liquefaction.
2. The potential for liquefaction on level ground shall be
determined on the basis of the structural occupancy categories associated with the uncorrected standard penetration resistance (N) at the site, as defined in Figure
1813.1, or a site-specific analysis performed by an engineer with specific expertise in the evaluation of liquefaction.
1813.2 Site-specific analyses. In evaluating liquefaction
potential, the analysis shall consider the following parameters:
ground surface acceleration, earthquake magnitude, magnitude scaling factor, effective overburden pressure, hammer
energy, cone penetration resistance (where applicable), and
fines content. If a site response analysis is conducted, bedrock
acceleration time histories and a shear wave velocity profile
based on in-situ measurements may be utilized. These analyses
may consider the results of laboratory cyclic shear tests.
1813.3 Foundation design analysis. The foundation design
analysis shall consider an assessment of potential consequences of any liquefaction and soil strength loss including
estimation of differential settlement, lateral movement or
reduction in foundation soil-bearing capacity, and may incorporate the potential benefits of any proposed mitigation measures. Such measures may be given consideration in the design
of the structure and can include, but are not limited to, ground
improvement, pore pressure dissipation, selection of appropriate foundation type and depths, selection of appropriate structural systems to accommodate anticipated displacements, or
any combination of these measures.
1812.10 Dewatering. Where piers are carried to depths below
water level, the piers shall be constructed by a method that will
provide accurate preparation and inspection of the bottom in
dry conditions.
In evaluating the potential for liquefaction, the effect of settlements induced by seismic motions and loss of soil strength
shall be considered. The analysis performed shall incorporate
the effects of peak ground acceleration, appropriate earthquake
magnitudes and duration consistent with the design earthquake
ground motions as well as uncertainty and variability of soil
properties across the site. Peak ground acceleration, seismically induced cyclic stress ratios and pore pressure development may be determined from a site-specific study taking into
account soil amplification effects and ground motions appropriate for the seismic hazard. Other recognized methods of
analysis may be used in the evaluation process subject to the
approval of the commissioner. Effects of pore water pressure
buildup shall be considered in the design except for the following conditions:
1812.11 Method of construction. Methods of construction
shall conform to ACI 336.1 “Standard Specification for the
Construction of Drilled Piers.”
1. The calculated cyclic shear demand is equal to or less
than 75 percent of the calculated cyclic shear strength for
Structural Occupancy Category I, II and III structures.
1812.9 Steel shell. Where concrete piers are entirely encased
with a circular steel shell, and the area of the shell steel is considered reinforcing steel, the steel shall be protected under the
conditions specified in Section 1808.2.17. Horizontal joints in
the shell shall be spliced to comply with Section 1808.2.7.
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2. The calculated cyclic shear demand is equal to or less
than 85 percent of the calculated cyclic shear strength for
Structural Occupancy Category IV structures.
during construction and for as long as necessary after construction concludes, as determined by the commissioner.
1813.4 Design considerations. At sites where liquefaction is
determined to be probable, the following considerations shall
be in the design:
1. Liquefiable soils shall be considered to have no passive
(lateral) resistance or bearing capacity value during an
earthquake, unless shown otherwise by accepted methods of analysis. The engineer shall submit an analysis for
review and approval by the commissioner, demonstrating that the proposed construction is safe against the
effects of soil liquefaction.
2. Where liquefiable soils are present in sloped ground or
over sloped nonliquefiable substrata and where lateral
displacement is possible, the engineer shall submit a stability analysis for review and approval by the commissioner, demonstrating that the proposed construction is
safe against failure of the soil and that the effect of potential lateral displacements are acceptable.
SECTION BC 1814
UNDERPINNING
1814.1 General. Where the protection and/or support of adjacent structures is required, an engineer shall prepare a preconstruction report summarizing the condition of the structure as
determined from examination of the structure, the review of
available design documents and if necessary, the excavation of
test pits. The engineer shall determine the requirements for
underpinning and protection and prepare site-specific plans,
details, and sequence of work for submission to the commissioner. Such support may be provided by underpinning, sheeting, and bracing, or by other means acceptable to the
commissioner. Underpinning piers, walls, piles and footings
shall be designed and installed in accordance with provisions
of this chapter and Chapter 33 and shall be inspected in accordance with provisions of Chapter 17.
1814.1.1 Underpinning and bracing. Where underpinning is used for the support of adjacent structures, the piers,
wall piles or footings shall be installed in such manner so as
to prevent the lateral or vertical displacement of the adjacent
structure, to prevent deterioration of the foundations or
other effects that would disrupt the adjacent structure. The
sequence of installation and the requirements for sheeting,
preloading, wedging with steel wedges, jacking or dry
packing shall be identified in the design.
1814.2 Use of rock support in lieu of underpinning. Existing
structures founded at a level above the level of adjacent new
construction may be supported on Class1a and 1b rock in lieu
of underpinning, sheeting and bracing or retaining walls, provided that a report by the engineer substantiates the safety of
the proposed construction. The engineer shall also certify that
the he or she has inspected the exposed rock and the jointing
therein and has determined whether supplemental support of
the rock face is required.
1814.3 Monitoring of influenced structures. A land surveyor
or engineer shall monitor the behavior of influenced structures
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FIGURE 1813.1
LIQUEFACTION ASSESSMENT DIAGRAM
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